Philosophical Transactions/Volume 1/Number 14

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Num. 14.



Munday, July 2. 1666.

The Contents.

An Account of a New kind of Baroscope, which may be call'd Statical; and of some Advantages and Conveniencies it hath above the Mercurial; communicated by Mr. Boyle.The Particular Observations of the planet Mars, formerly intimated to have been made by Mr. Hook in February and March last.Some Observations, made in Italy, confirming the former; and withall fixing the Period of the said Planet's Revolution.Observations, lately made at London, of the Planet Jupiter: as also of Saturn. A Relation of a sad Effect of Thunder and Lightning.An Account of some Books, lately publish't; videl. The Relations of divers Curious Voyages, by Mons. Thevenot:A Discourse about the Cause of the Inundation of the Nile, by Mons. de la Chambre; both French:De Principiis & Ratiocinatione Geometrarum, Contra Fastum Professorum Geometriæ, by Mr. Hobbes:King Salomons Pourtraiture of Old Age, by J. Smith, M.D.

An Account

of a New kind of Baroscope, which may be call'd Statical; and of some Advantages and Conveniencies it hath above the Mercurial: communicated, some while since, by the Honourable Robert Boyle.

AS for the New kind of Baroscopes, which, not long agoe,**See Num. 11. p. 185. Phil. Transactions. I intimated to you, that my haste would not permit me to give you an account off; since your Letters acquaint me, that you still design a Communicating to the Curious as much Information, as may be, in reference to Baroscopes; I shall venture to send you some Account of what I did but name (in my former Letter) to you.

Though by a Passage, you may meet with in the 19th and 20th Pages of my Thermometrical Experiments and Thoughts, you may find, that I did some years agoe think upon this New kind of Baroscope; yet the Changes of the Atmosphere's Weight not happening to be then such, as I wish'd, and being unwilling to deprive my self of all other use of the exactest Ballance *, * The Scales here meant were before competent Eye-witnesses made to turn manifestly with the thousandth part of a grain. that I (or perhaps any man) ever had, I confess to you, that successive avocations put this attempt for two or three years out of my thoughts; till afterwards returning to a place, where I chanc'd to find two or three pairs of Scales, I had left there, the fight of them brought it into my mind; and though I were then unable to procure exacter, yet my desire to make the Experiment some amends for so long a neglect, put me upon considering, that if I provided a Glass-buble, more than ordinary large and light, even such Ballances, as those, might in some measure perform, what I had tried with the strangely nice ones above-mention'd.

I caused then to be blown at the Flame of a Lamp some Glass-bubles as large, thin and light, as I could then procure, and choosing among them one, that seem'd the least unfit for my turn, I counterpoised it in a pair of Scales, that would loose their Æquilibrium with about the 30th part of a Grain, and were suspended at a Frame. I placed both the Ballance and the Frame by a good Baroscope, from whence I might learn the present weight of the Atmosphere. Then leaving these Instruments together; though the Scales, being no nicer than I have express'd, were not able to shew me all the Variations of the Air's weight, that appear'd in the Mercurial Baroscope, yet they did what I expected, by shewing me variations no greater, than alter'd the height of Quicksilver half a quarter of an Inch, and perhaps much smaller, than those: Nor did I doubt, that, if I had had either tender Scales, or the means of supplying the Experiment with convenient accommodations, I should have discerned far smaller Alterations of the Weight of the Air, since I had the pleasure to see the Buble sometimes in an æquilibrium with the counterpoise; sometimes, when the Atmosphere was high, preponderate so manifestly, that the Scales being gently stirr'd, the Cock would play altogether on that side, at which the Buble was hung; and at other times (when the Air was heavier) that, which was at the first but the Counterpoise, would preponderate, and, upon the motion of the Ballance, make the Cock vibrate altogether on its side. And this would continue sometimes many daies together, if the Air so long retain'd the same measure of gravity; and then (upon other changes) the Buble would regain an æquilibrium, or a preponderance; so that I had oftentimes the satisfaction, by looking first upon the Statical Baroscope (as for distinctions sake it may be call'd) to foretell, whether in the Mercurial Baroscope the Liquor were high or low. Which Observations though they hold as well in Winter, and several times in Summer (for I was often absent during that season) as the Spring, yet the frequency of their Vicissitudes (which perhaps was but accidental) made them more pleasant in the latter of these seasons.

So that, the matter of Fact having been made out by variety of repeated Observations, and by sometimes comparing severall of those new Baroscopes together, I shall add some of those Notes about this Instrument, which readily occur to my memory, reserving the rest till another opportunity.

And First, if the ground, on which I went in framing this Baroscope, be demanded, the answer in short may be; 1.That, though the Glass-buble, and the Glass-counterpoise, at the time of their first being weigh'd, be in the Air, wherein they both are weigh'd, exactly of the same weight; yet they are nothing near of the same bulk; the Buble, by reason of its capacious cavity (which contains nothing but Air, or something that weighs less than Air) being perhaps a hundred or two hundred times (for I have not convenience to measure them) bigger than the Metal line counterpoise. 2.That according to a Hydrostatical Law (which you know I have lately had occasion to make out) If two Bodies of equal gravity, but unequal bulk come to be weigh'd in another Medium, they will be no longer equiponderant; but if the new Medium be heavier, the greater Body, as being lighter in Specie, will loose more of its weight, than the lesser and more compact; but if the new Medium be lighter than the first, then the bigger Body will outweigh the lesser: And this disparity, arising from the change of Medium's, will be so much the greater, by how much the greater inequality of bulk there is between the Bodies formerly equiponderant. 3.That, laying these two together, I consider'd, that 'twould be all one, as to the effect to be produced, whether the Bodies were weighed in Medium's of differing gravity, or in the same Medium, in case its (specifick) gravity were considerably alter'd; And consequently, that since it appear'd by the Baroscope, that the weight of the Air was sometimes heavier, and sometimes lighter, the alterations of it, in point of gravity, from the weight, it was off at first counterpoising of the Buble of it, would unequally affect so large and hollow a Body, as the Buble, and so small and dense a one, as a Metallin weight; And when the Air by an increase of gravity should become a heavier Medium, than before, it would buoy up the Glass more than the Counterpoise; and if it grew lighter, than it was at first, would suffer the former to preponderate: (The Illustrations and Proof can scarce be added in few words; but, if it be desired, I may, God permitting, send you them at my next leasure:) And though our English Air be about a thousand times lighter, than water, the difference in weight of so little Air, as is but equal in bulk to a Buble, seem'd to give small hopes, that it would be sensible upon a Ballance; yet, by making the Buble very large and light, I supposed and found the Event, I have already related.

Secondly, The hermetically seal'd Glass-buble, I employed, was of the bigness of a somewhat large Orange, and weigh'd about 1. drachme and 10 grains. But I thought it very possible, if I had been better furnish't with conveniences (wherein I afterwards found, I was not mistaken) to make (among many, that might be expected to miscarry) some, that might be preferable to this, either for capacity or lightnes, or both; especially if care be taken, that they be not seal'd up, whilst they are too hot. For, though one would think, that it were contagious to rarify and drive out the Air as much as is possible, because in such seal'd Bubles the Air it self (as I have elsewhere shewn) has a weight; yet this advantage countervails not the inconvenience of being obliged to increase the weight of the Glass, which when it includes highly ratified Air, if it be not somewhat strong, will be broken by the pressure of the External Air, as I have sufficiently tryed.

Thirdly, I would have tryed, whether the Dryness and Moisture of the Air would in any measure have alter'd the weight of the Buble, as well as the Variation of Gravity produced in the Atmosphere by other causes; but the extraordinarily constant absence of Fogs, kept me from making Observations of this kind; save that one morning early, being told of a mist, I sent to see (being my self in bed) whether it made the Air so heavy as to buoy up the Buble; but did not learn, that that mist had any sensible operation on it.

Fourthly, By reason of the difficulties and casualties, that may happen about the procuring and preferring such large and light Bubles, as I have been lately mentioning; it may in some cases prove a convenience to be inform'd; That I have sometimes, instead of one sufficiently large Buble, made use of two, that were smaller. And, though a single Buble of competent bigness be much preferable, by reason, that a far less quantity and weight of Glass is requisite to comprise an equal capacity, when the Glass is blown into a single Buble, than when it is divided into two; yet I found, that the employing of two instead of one, did not so ill answer my expectations, but that they may for a need serve the turn instead of the other; than which they are more easier to be procured: And if the Ballance be strong enough to bear so much Glass, without being injur'd; by employing two or a greater number of large Bubles, the effect may be more conspicuous, than if only a single Buble (though a very good one) were employed.

This instrument may be much improved by divers Accommodations. As

First, There may be fitted to the Ansa (or Checks of the Ballance) an Arch (of a Circle) divided into 15. or 20. deg. (more or less, according to the goodness of the Ballance) that the Cock resting over against these Divisions, may readily and without Calculation shew the quantity of the Angle, by which, when the scales propend either way, the Cock declines from the Perpendicular, and the beam from its Horizontall parallelism.

Secondly, Those, that will be so curious, may, instead of the Ordinary Counterpoise (of Brass) employ one of Gold, or at least of Lead, whereof the latter being of equal weight with Brass, is much less in Bulk, and the former amounts not to half its bigness.

Thirdly, These parts of the Ballance, that may be made of Copper or Brass, without any prejudice to the exactness, will, by being made of one of those Mettals, be less subject, than Steel, (which yet, if well hardned and polish'd, may last good a great while) to rust with long standing.

Fourthly, Instead of the scales, the Buble may be hung at one end of the Beam, and only a Counterpoise to it at the other, that the Beam may not be burthen'd with unnecessary weight.

Fifthly, The whole instrument, if placed in a small Frame, like a square Lanthorn with Glass-windows, and a hole at the top for the Commerce of the internal and external Air, will be more free from dust, aud irregular agitations; to the latter of which, it will otherwise be sometimes incident.

Sixthly, This instrument being accommodated with a light Wheele and an Index (such as have been applyed by the excellent Dr. Chr. Wren to open Weather glasses, and by the ingenious Mr. Hook to Baroscope) may be made to shew much more minute variations, than otherwise.

Seventhly, And the length of the Beam, and exquisitness of the Ballance, may easily, without any of the foregoing helps (and much more with them) make the instrument far exacter, than any of those, I was reduced to employ. And to these Accommodations divers others may be suggested by a farther consideration of the nature of the thing, and a longer practice.

Tough in some respects this Statical Baroscope be inferior to the Mercurial; yet in others it has its own advantages and conveniences above it.

And 1.It confirms ad oculum our former Doctrine, that the falling and rising of the Mercury depends upon the varying weight of the Atmosphere; since in this Baroscope it cannot be pretended, that a Fuga vacui, or a Funiculus, is the cause of the changes, we observe.2. It shews, that not only the Air has weight, but a more considerable one, than some Learned men, who will allow me to have prov'd, it has some weight, will admit; since even the variation of weight in so small a quantity of Air, as is but equal in bulk to an Orange, is manifestly discoverable upon such Ballances, as are none of the nicest.3. This Statical Baroscope will oftentimes be more parable, than the other: For many will finde it more easie, to procure a good pair of Gold-scales, and a Buble or two, than a long Cane seal'd, a quantity of Quick-silver, and all the other requisits of the Mercurial Baroscope; especially if we comprise the trouble and skill, that is requisite to free the deferred part of the Tube from Air.4. And whereas the difficulty of removing the Mercurial Instrument has kept men from so much as attempting to do it, even to neighbouring places; the Essential parts of the Scale-Baroscope (for the Frame is none of them) may very easily in a little room be carried, whither one will, without the hazard of being spoil'd or injur'd.5. There is not in Statical Baroscopes, as in the other, a danger of uncertainty, as to the goodness of the Instruments, by reason, that in these the Air is, in some more, and in some less perfectly excluded; whereas in those, that consideration has no place. (And by the way, I have sometimes, upon this account, been able to discover by our new Baroscope, that an esteem'd Mercurial one, to which I compared it, was not well freed from Air.) 6. It being, as I formerly intimated, very possible to discover Hydrostatically, both the bigness of the Buble, and the Contents of the cavity, and the weight and dimensions of the Glassie substance (which together with the included Air make up the Buble,) much may be discover'd by this Instrument, as to the Weight of the Air, Absolute or respective. For, when the Quick-silver in the Mercurial Baroscope is either very high, or very low, or at a middle station between its greatest: and least height, bringing the Scale-Barometer to an Exact Æquilibrium; (I with very minute divisions of a Graine,) you may, by watchfully observing, when the Mercury is risen or faln just an inch, or a fourth, or half an inch &c. and putting in the like minute divisions of a Grain to the lighter Scale, till you have again brought the Ballance to an exquisit Æquilibrium; you may, I say, determine, What known weight in the Statical Baroscope answers such determinate Altitudes of the ascending and descending Quick-silver in the Mercurial. And if the Ballance be accommodated with a divided Arch, or a Wheel and Index, these Observations will assist you for the future to determine readily, by seeing the inclination of the Cock or the degree mark'd by the Index, what pollency the Buble hath, by the change of the Atmospheres weight, acquired or lost. Some Observations of this nature I watchfully made, sometimes putting in a 64th sometimes a 32th sometimes a 16th and sometimes heavier parts of a Grain, to the lighter Scale. But one, that knew not, for what uses those little papers were, coming to a window, where my Baroscopes stood, so unluckily shook them out of the Scales, and confounded them, that he robb'd me of the opportunity of making the nice Observations I intended, though I had the satisfaction of seeing, that they were to be made. 7. By this Statical Instrument we may be assisted to compare the Mercurial Baroscopes of several places (though never so distant) and to make some Estimates of the Gravities of the Air therein. As if, for instance, I have found by Observation, that the Buble, I employ, (and one may have divers Bubles of several sizes, that the one may repaire any mischance, that may happen to another) weigh'd just a Drachme, when the Mercurial Cylinder was at the height of 291/2 inches (which in some places I have found a moderate altitude;) and that the Addition of the 16th part of a gr. is requisite to keep the Buble in an Æquilibirum, when the Mercury is risen an 8th, or any determinate part of an inch above the former station: When I come to another place, where there is a Mercurial Barometer, as well freed from Air as mine (for that must be supposed) if taking out my Scale instrument, it appeare to weigh precisely a Drachme, and the Mercury in the Baroscope there stand at just 291/2 inches, we may conclude the Gravity of the Atmosphere not to be sensibly unequal in both those two places, though very distant. And though there be no Baroscope there, yet if there be an additional weight, as for instance, the 16th part of a Grain requisite to be added to the Buble, to bring the scales to an Æquilibrium, it will appear that the Air at this second place is, at that time so much heavier, than the Air of the former place was, when the Mercury stood at 291/2 inches.

But in making such comparisons, we must not forget to consider the Situation of the several places, if we mean to make Estimates not only of the weight of the Atmosphere, but of the weight and density of the Air. For, though the Scales wil shew (as has been said) whether there be a difference of weight in the Atmosphere at the two places; yet, if one of them be in a Vale or bottom, and the other on the top or some elevated part of a Hill, it is not to be expected, that the Atmosphere, in this latter place, should gravitate as much, as the Atmosphere in the former, on which a longer Pillar of Air does lean or weigh.

And the mention, I have made of the differing Situation of Places, puts me in mind of something, that may prove another use of our Statical Baroscope, and which I had thoughts of making tryal ofl, but was Accidentally hindred from opportunity of doing it. Namely, that by exactly poysing the Buble at the foot of a high Steeple or Hill, and carrying it in its close Frame to the top, one may, by the weight requisite to be added to Counterpoise there to bring the Beam to its Horizontal position, observe the difference of the weight of the Air at the bottom, and at the top; and, in case the Hill be high enough, at some intermediate Stations. But how far this may assist men, to estimate the Absolute or Comparative height of Mountains, and other elevated Places; and what other Uses the Instrument may be put to, when it is duly improved; and the Cautions, that may be requisite in the several cases, that shall be proposed, I must leave to more leasure, and farther Consideration.

The Particulars. Of those Observations of the Planet Mars, formerly intimated to have been made at London in the Months of February and March A. 1665/6.

To perform what was promised Num. 11. of these Papers pag. 198; 'tis thought fit now to publish the Particular Observations, concerning the spots in Mars, and their motion, as they were made with a 36 foot Telescope, and produced in writing before the Royal Society, the 28 March 1666. by Mr. Hook, as follows;

Having a great desire (saith he) to observe the Body of Mars, whilst Acronycal and Retrograde (having formerly with a Glass of about 12. foot long, observ'd some kind of Spots in the Face of it,) though it be not at present in the Perihelium of its Orbe, but nearer its Aphelium, yet I found, that the Face of it, when neer its Opposition to the Sun (with a Charge, the 36. foot glass, I made use off; would well bear) appear'd very near as big, as that of the Moon to the naked eye; which I found, by comparing it with the Full Moon, near adjoining to it, March 10.

But such had been the ill disposition of the Air for several nights, that from more than 20. Observations of it, which I had made since its being Retrograde, I could find nothing of Satisfaction, though I often imagin'd, I saw Spots, yet the Inflective veins of the Air (if I may so call those parts, which, being interspers'd up and down in it, have a greater or less Refractive power, than the Air next adjoining, with which they are mixt) did make it so confus'd and glaring, that I could not conclude upon any thing.

On the third of March, though the Air were still bad enough yet I could see now and then the Body of Mars appearing of the form A: which I presently described by Scheme; and about 10. minutes after, as exactly representing what I saw through the Glass, as I could, I drew the Scheme B. This I was sufficiently satisfied (by very often observing it through the Tube, and changing my Eye into various positions, that so there might be no kind of Fallacy in it) could be nothing else, but some more Dusky and Spotted parts of the Face of this Planet.

March 10. finding the Air very bad, I made use of a very shallow Eye-glass, as finding nothing Distinct with the greater Charge; and saw the appearance of it as in C, which I imagin'd, might be the Representation of the former Spots by a lesser charge. About 3 of the Clock the same morning, the Air being very bad (though to appearance exceeding clear, and causing all the Stars to twinckle, and the minute Stars to appear very thick) the Body seem'd like D; which I still suppos'd to be the Representation of the same Spots through a more confused and glaring Air.

But observing March 21. I was surprised to find the Air (though not so clear, as to the appearance of small Stars) so exceeding transparent, and the Face of Mars so very well defined, and round, and distinct, that I could manifestly see it of the shape in E. about half an hour after Nine at night; The Triangular spot on the right side (as it was inverted by the Telescope, according to the appearances, through with all the preceeding Figures are drawn) appear'd very black and distinct, the other towards the left more dim; but both of them sufficiently plain and defin'd. About a quarter before 12. of the Clock the same night, I observ'd it again with the same Glass, and found the appearance exactly, as in F; which I imagin'd to shew me a Motion of the former triangular spot: But designing to observe it again about 3. of the Clock the same Morning, I was hindred by cloudy weather.

But March 22. about half an hour after 8. at night, finding the same Spots in the same posture, I concluded, that the preceding Observation was only the appearance of the same Spots at another height and thickness of the Air: And thought my self confirm'd in this Opinion, by finding them in much the same posture, March 23. about half an hour after 9. though the Air was nothing so good as before.

And though I desired to make Observations, about 3. of the Clock those mornings; yet something or other interven'd, that hindred me, till March 28. about 3 of the Clock, the Air being light (in weight) though moist and a little hazy; when I plainly saw it, to have the form, represented in I; which is not reconcileable with the other Appearances, unless we allow a Turbinated motion of Mars upon its Center: Which, if such there be, from the Observations made March 21. 22. and 23. we may guess it to be once or twice in about 24. hours unless it may have some kind of Librating motion; which seems not so likely. Now, whether certainly so or not, I shall endeavour, as oft as I have opportunity, further to observe.

A particular direction to the Figures mentioned in the precedent discourse.

Figure A-I

A. March 3d. 00h. 20m. in the morning: the Air having many parts dispersed up and down in it; by the Wheel Barometer, heavy.

B. Another Scheme, which I drew from my Observation, about 10. minutes after, the same morning. Both these were observed with a very deep Eye-glass.

C. March 10d 00h 20m in the morning: the Air heavy and inflective. Use was made of a shallow or ordinary Charge.

D. March 10d 3h 00m in the Morning; the Air very heavy and inflective, which made it glare and radiate, and be more confused, than about 3. hours before. A shallow Charge.

E. March 21d 91/2h post merid; the Air light (in weight) and clear, without inflecting parts; the Face appear'd most distinctly of this Forme. A shallow Charge.

F. March 21d 113/4h post merid; the Air continuing very light and clear, without inflecting vapours. A shallow Charge.

G. March 21d 81/2h post mer. the Air clear, with very few inflecting veins in it, and indifferent light. A shallow Charge.

H. March 23d 91/2h post mer. the Air pretty light but moist, and somewhat thick and hazy, but seem'd to have but few veins, or inflecting parts.

I. March 28d 3h p. m. much the same kind of Air with that of March 23, light, moist, and a little hazy, with some very few veins.


Made in Italy, confirming the former, and withall fixing the Period of the Revolution of Mars.

These Observations we shall summarily present the Curious in these parts with, as they were lately presented (by Letter from his Excellency the Ambassadour of Venice, now residing at the Court of France) to the Royal Society, in some printed sheets of Paper, entituled, MARTIS, circa Axem Proprium Revolubilis, Observationes, BONONIÆ à JO. DOMINICO CASSINO habitæ; come to hand June 3. 1666.

In these Papers the Excellent Cassini affirms;

1 . That with a Telescope of 24. Palmes, or of about 16 Foot, wrought after S. Campani's way, he began to observe February 6. 1666 (st.n.) in the morning, and saw two dark Spots in the first Hace of Mars.

2. That with the same Glass he observ'd Febr. 14/24 the Evening, in the other Face of this Planet, two other Spots, like those of the first, but bigger.

3. That afterwards continuing the Observations, he found the Spots of these two Faces to turn by little and little from East to West, and to return at last to the same situation, wherein he had seen them first.

4. That S. Campani, having also observ'd at Rome with Glasses of 50. Palmes or about 35 Foot, likewise of his own contrivance, had seen in the same Planet the same Phenomena.

4. That sometimes he hath seen, during the same night, the two Faces of Mars, one, in the Evening, the other in the Morning.

6. That the Motion of these Spots in the inferior part of the apparent Hemisphere of Mars, is made from East to West, as that of all the other Celestial Bodies, and is perform'd by Parallels, that decline much from the Equator and little from the Ecliptick.

7. That the Spots return the next day to the same situation, 40. minuts later, than the day before; so that in every 36. or 37. daies, about the same hour, they come again to the same place.

8. He promises shortly to give us the particular Tables of this Motion and of its Inequalities, together with the Ephemerides themselves.

9. He represents, that some other Astronomers have also made at Rome several Observations of these Spots of Mars, from March 14/24. to March 20/30 with Glasses, wrought by Eustachio Divini, of 25. and 45. Palmes: Which Spots he makes little differing from his own, of the first Face; as will by and by appear, by the direction to the Schemes.

10. But he adds, that those other Roman Astronomers, that have observ'd with Divini's Glasses, will have the Conversion of Mars to be performed, not in 24 h, 40 m. (as he maintains it is) but in about 13 h.

11. And to evince, that they are mistaken in these Observations of theirs; he alledges, That they assure that the Spots, which they have seen in this Planet, (by an Eustachian Telescope) the 20/30 March, were small, very distant from one another, remote from the middle of the Disk, and the Oriental Spot was less, than the Occidental (as is represented by the Fig. O; like that of the first Face of Mars) whereas, on the contrary, He (Cassini) pretends to evidence by his Observations, made at the same time at Bononia, that, the same day and hour, those Spots were very large, neer one another, in the midst of the Disk, the Oriental bigger than the Occidental (as appears by Fig. P, which is that of the second Face of Mars.)

12. Besides, he declares, that those Astronomers were too hasty, in determining, after 5 or 6 Observations only, in how much time Mars finish's his Revolution; and denies it to be perform'd in 13 hours: adding, that, though Himself had observ'd for a much longer time, than they; yet he durft not for a great while define, Whether Mars made but one Turn in 24 hours 40 minuts or two; and that all, that he could, for a long time affirm, was onely this, that after 24 h. 40 m. this Planet appear'd in the same manner he did before.

13. But since those first Observations, He affirms to have found cause to determine, that the Period of this Conversion is made in the said space of 24 h. 40 m; and not oftner than once within that time; Alledging for proof;

1. That, whereas Febr. 6. (st.n.) he saw the Spots of the first Face of Mars, moving from eleven of the Clock in the night, until break of day, they appear'd not afterwards in the Evening after the rising of that Planet (witness several intelligent persons, which he names, that were present at the Observations) Whence he infers, that after 12 hours and 20 minuts, the same Spots did not come about; since that the same, which in the morning were seen in the middle, upon the rising of Mars; after 13 or 14 hours, might have appear'd neer the Occidental Limb. But, because he might be imposed upon by Vapors, whilst Mars was yet so neer the Horizon, he gives this other determination, vid.

2. Whereas he saw the first Face of Mars the 6 of February at 11 of the clock of the night following; he did not see the same after 18 daies at the same hour; as he ought to have done, if the Period were absolved in the space of 12 h. 20 m.

3. Again, whereas he saw Febr. 24. in the Evening, the other face of Mars, he could not see the same, the 13. and 15. day of March, to wit after 17 and 19 days; as he should have done, if the Revolution were made in the newly mention'd time.

4. Again, whereas the 27. of March in the Evening he saw the second Face of Mars, he could not see it the 14. and 16. of April.

From all which Observations he Judges it to be evident, that the Period of this Planets Revolution is not perform'd in the space of 12. hours 20. minutes, but in about 24. hours 40 minutes; more exactly to be determin'd by comparing distant Observations: And that those who affirm the former, must have been deceived by not well distinguishing the two Faces, but that having seen the second, taken it for the first.

All which he concludes with this Advertisement, that, when he defines the time of the Revolution of Mars, he does not speak of its Mean Revolution, but onely of that, which he observ'd, whilst Mars was opposite to the Sun; which is the shortest of all.

The Figures of the Principal Observations, represented in the Book here discoursed of, may be seen in the annexed Scheme; videl.
Figure K-P

K. One of the Faces of Mars, as S. Cassini observed it March 3. (st.n) 1666 in the Evening, with a Glass of 24 Palmes.

L. The other Face, as he saw it Febr. 14/24 in th Evening.

M. The first Face, as S. Campani saw at Rome, March 3. 1666, in the Evening, with a Glass of 50 Palmes.

N. The second Face, as the same Campani observ'd it March 18/28 in the Evening.

O. The Figure of Mars, as it was seen at Rome by a Telescope of Divini of 45 Palmes, March 20/30.

P. The Figure of the said Planet, as it was seen the same day and hour at Bononia by Cassini; being that of the second Face.

Some Observations made at London concerning the Planet Jupiter.

These, as they were made, so they were imparted, by Mr. Hook, as follows:

Figure Q

A. 1666. June 26. between 3. and 4. of the Clock in the morning, I observed the Body of Jupiter through a 60. foot glass, and found the apparent Diameter of it through the Tube, to be somewhat more than 2. degrees, that is, about four times as big, as the Diameter of the Moon appears to the naked Eye. I saw the Limb pretty round, and very well defin'd without radiation. The parts of the Phasis of it had various degrees of Light. About a and f, the North and South poles of it (in the Fig. Q) 'twas somewhat darker, and by degrees it grew brighter towards b. and e, two Belts or Zones; the one of which (b) was a small dark Belt crossing the Body Southward; Adjoyning to which was a smal Line of a somewhat lighter part; and below that again, Southwards, was the great black Belt c. Between that, and e, the other smaller black Belt, was a pretty large and bright Zone but the middle d, was somewhat darker than the edges. I perceiv'd, about 3h 15m near the middle of this, a very dark round Spot, like that represented at g, which was not to be perceiv'd about half an hour before: And I observed it, in about 10. minutes time to be gotten almost to d, keeping equal distance from the Satelles h, which moved also Westwardly, and was joyn'd to the Disk at i, at 3h 25m. After which, the Air growing very hazy, and (as appeared by the Baroscope) very light also (in weight) I could not observe it: So that it was sufficiently evident, that this black Spot was nothing else, save the shadow of the Satelles h, Eclipsing a part of the Face of Jupiter. About two hours before, I had observed a large darker spot in the bigger Belt about k, which in about an hour or little more (for I did not exactly observe the time, nor draw the Figure of it) moving Westwards, disappear'd. About a week before, I discover'd also, together with a Spot in the Belt c. another Spot in the Belt e, which kept the same way and velocity with that of the Belt c. The other three Satellites in the time of this Eclipse, made by the Satelles, were Westwards of the Body of Jupiter; appearing as bright through the Tube, as the Body of Jupiter did to the naked Eye, and I was able to see them longer through the Tube, after the day-light came on, than I was able to see the Body of Jupiter with my naked eye.

A late Observation about Saturn made by the same.

Figure R

June 29 1666. between 11. and 12. at night I observed the Body of Saturn through a 60. foot Telescope, and found it exactly of the shape represented in the Figure R. The Ring appear'd of a somewhat brighter Light than the Body; and the Black lines a a, crossing the Ring, and b b crossing the Body (whether Shadows or not, I dispute not) were plainly visible; whence I could manifestly see, that the Souther most part of the Ring was on this side of the Body, and the Northern part, behind, or covered by the Body.

A Relation
Of a sad effect of Thunder and Lightning

This Relation was written by that worthy Gentleman, Thomas Neale Esquire, (the then High Sheriff of the County of Hampshire, when this disaster hapned) to a Friend of his in London, as follows;

On the 24 of January 1665/6, one Mr. Brooks of Hampshire, going from Winchester towards his house near Andover in very bad Weather, was himself slain by Lightning, and the Horse, he rode on, under him. For about a mile from Winchester he was found with his Face beaten into the ground, one leg in the stirrup, the other in the Horses mane; his Cloaths all burnt off his back, not a piece as big as a handkerchief left intire, and his hair and all his body singed. With the force, that struck him down, his nose was beaten into his face, and his Chin into his Breast; where was a wound cut almost as low, as to his Navil; and his cloaths being, as aforesaid, torn, the pieces were so scatter'd and consum'd, that not enough to fill the crown of a hat could be found. His gloves were whole. but his hands in them sing'd to the bone. The hip-bone and shoulder of his Horse burn't and bruised; and his saddle torn in little pieces. This was what appear'd to the Coroners inquest, and so is likely to be as near truth, as any is to be had.

So far this Letter: Which, if it had come soon enough to the hands of the Publisher, would have been joyned to a like Relation, inserted in the next foregoing Papers (Num. 13.) of an accident hapn'd at a later time. With both which may be compared the Account, formerly published in Latin by the Learned Dr. Charleton, concerning the Boy, that was

struck near Nantwich in Cheshire; the Title of the Book being, Anatome Pueri de Cælo tacti: such Relations, when truly made, well deserving to be carefully recorded for farther consideration.

Of some Books lately publish't

RELATIONS OF DIVERS CURIOUS VOYAGES, by Mons. Thevenot; the third Tome in French. This book contains chiefly, the Ambassie of the Dutch into China, translated out of the Dutch manuscript; A Geographical description of China, translated out of a Chinese Author by Martinius; And the Account, which the Directors of the Dutch East-India Company made to the States General, touching the state of affairs in the East-Indies, when their late Fleet parted from thence. To touch some things of a Geographical and Philosophical nature, contained therein, we shall take notice;

1. How the Kingdom of China is peopled; there being according to the best computation (which is there made with singular care) above 58 millions of Men, not counting Magistrates, Soldiers, Priests, Eunuchs, Women and Children; so that it may not be altogether strange, if one should affirm, there were 200 millions of people, of all sorts, in that Kingdom.

2. That Catay is nothing else, but the Six Northern Provinces of China, separated from the other Nine, by the great River KIANG; and that the City Cambalu is the same with that of Peking: the Tartars, who carry every three years their Tribute to the Emperor of China, constantly calling the said Provinces and City by those names of Catay and Cambalu.

3. That China is so well furnisht with Rivers, and cut Channels, that men may go from the most Southern to the most Northern part thereof by water, except one daies journey; as the Dutch Ambassadours did, embarking at Canton, which is 23 d. 43 m. Northern Latitude, and landing at Peking, which is about 40 d; having only travell'd one daies journey over some Mountains of the Province Kiamsi.

4. That the people of China are exceeding industrious Husbandmen making, among other waies of improving their soils, great use of Flouding.

5. That the Physicians of China do cure Sickness with much ease, and in a short time: That they have very ancient Books of the nature and vertues of Herbs, Trees and Stones: That their Modern Physicians (as well as their Ancient ones did) write of the Prognosticks, Causes, Effects, &c. of Diseases. That their Remedies consist for the most part of Simples and Decoction, Cauteries, Frictions; without the use of Bloud-letting: That they have such an excellent skill and method in feeling the Pulse, that by the means thereof they discover even the most latent causes of Diseases; taking a good half hour, when they visit a Patient, in feeling and examining his Pulse: That they prescribe much the use of The; and the drinking alwayes warme; whatever they drink: To the custome of both which it's imputed, that the inhabitants of China do spit very little, nor are subject to the Stone or Gout: That they prise highly the Root Ginseng, as an extraordinary Restorative and Cordiall, recovering frequently with it agonizing persons; one pound of it being paid with 3 pounds of silver. As for their Chymists, (of which they have also good store) they go beyond ours, promising not only to make Gold, but to give Immortality.

6. That their Nobility is raised from Learning and Knowledge, without regard to Bloud or Parentage, excepting the Royall Family.

7. That in CHEKIAN, a maritime Province, whence is the shortest cut of China to Japan, is the best and plentifullest Silk-trade in the world: And that there every year the Mulberries are cutt, and kept down, that they grow not into Trees, for the easier gathering of the Leaves, there being a double Silk-harvest in that Country, as there is in severall other parts of the East-indies; (both which there is hope, will shortly be imitated in Virginia.)

8. That the way of making Porcelane is this: (Which is the rather inserted here, because it agrees so well with an Account, we received a while since from a very Curious and intelligent Person of Amsterdam.) There is in the Province of Nankin a Town, call'd Goesisol; whence they draw the Earth for Porcelaine, which is found between the Rocks of Mountains. This Earth they beat very small, and stamp it to a very fine Powder, and then put it into Tubs fill'd with water; where the finest part links to the bottom. Afterwards 'tis kneaded in the form of small Cubes, of the weight of about 3. Catti (a Catti being 20 Ounces.) These pieces thus wrought are sold to the people, that commonly in great numbers fetch them, coming from the Town Sintesimo (otherwise Jontiou) in the Province of Kiansy, being about 50 miles distant from Wotsing, neer the City KIANSY; which people transport them to their homes, and there bake them in this manner: They heat their Ovens well, for the space of 15 daies successively, and then keep them so close, that no Air may get in; and after 15 other daies are pass'd, they open the Oven in the presence of an Officer, who takes every fifth vessel of each fashion for the service of the Emperor: Which done, the rest is sold to those of Ucienien, whence it is transported all over the Country. So that the Earth is not prepared, in Nankin, where 'tis found, because the people of that Province have not the skill of working it, as the other above mention'd; who also alone have the Art of coloring it, which they keep as a great Secret, not teaching it to any, but their Children and next Kindred.

9. That Musk is nothing else, but the Testicles of a Beast like a Dear, found in the Province of Honan; and that, when tis good and unmixt, as it comes from the Animali, they sell it even in Nankin or Pekin, for 30. or 35. Teyls (that is, about so many Crowns) the Catti, or 20 ɮ

Many other curious informations might be borrow'd from this Author, concerning the Customs, Studies, Exercises of the Chinese; of the number of the people of each Province; of the Natural productions of the Earth and Rivers there; of the Structure and Antiquity of their Wall; of the Magnificence of their Porcelain Tower &c; but, remitting for these things to the Book it self, we shal only add a piece of Oeconomy, used by the Holland-Merchants in their Commerce with China; which is, that they dry abundance of Sage-leaves, role them up, and prepare them like The, and carrying it to China, as a rare drogue, get for one pound of it, fourtimes as much The.

A DISCOURSE ABOUT THE CAUSES OF THE INUNDATION OF THE NILE, in French. The Author of this Book is Monsieur dela Chambre, who being perswaded from several Circumstances, that accompany the Overflowing of this River, that it cannot proceed from Rain, ventures to assign for a Cause of it, and of all the other effects that happen at the time of its swelling, the Niter, wherewith that water abounds.

The discourse having six parts, the Author endeavours to shew in the

First, that the Waters of the Nile are Nitrous, explicating the Nature of Salt, and Saltpeter, and imputing the fertility of the Earth, as well as the fecundity of Animals, to Salt. Where he shews, that all things, that serve to improve Land, are full of Salt; and that 'tis observ'd, that grain steep'd in Vrine, before sowing, rises sooner, and becomes fuller and stronger, than else. Adding, that that, which renders the Seed of Animals prolific, is, that one of the Spermatick veins hath its Origine from the Emulgent, through which the Nitrous and Saline Serosities, that discharge themselves into the Kidneys and Bladder, do pass.

In the Second, he examins, what is Fermentation, and how 'tis perform'd; affirming, that, what thrusts forth Plants in the Spring, is, that the Earth being fermented by the Niter, it harbours, the Nitrous spirits insinuate themselves into their Pores.

In the Third he treats of all the Circumstances, observable in the Inundation of the Nile. 'Tis affirm'd, that 3 or 4 days before that River begins to overflow, all its water is troubled: that then there falls a certain Dew, which hath a fermenting vertue, and leavens a Paste exposed to the Air: that the Mud, which has been drawn out of the water, grows heavier, when the overflowing begins, then it was before, and that by the increase of the weight of that Mud, they judge of the greatness of the approaching inundation. The Author pretends, that the Niter, which the Nile is stored with, is the cause of all these strange effects, and of many others, by him alledged, For, saith he, when the Nitre is heated by the heat of the Sun, it ferments, and mingling with the water, troubles it, and swells it, and makes it pass beyond its banks; after the same manner, as the Spirits in new Wine render it troubled, and make it boyle in the vessel. And it seems not likely to him, that the Mud, found in the Nile, should come a far off; for then it would at last so raise the banks of this River, that it would not be able to overflow them any longer, Whereas 'tis more than 2000 years, that the banks thereof are not grown higher, there being now requisite but 16. cubits for overflowing the Land, no more than there was in the time of Herodotus. Which shews, saith he, that this Mud is nothing but a volatil Niter, which exhaling, doth not increase the Earth. As for the Ægyptian Dew, and the increase of the weight of the Mud, he adscribes them to the same Cause. For, the spirits of Nitre abounding in the Nile, when raised into the Air with the vapors, that exhale continually from this River, there is made out of their mixture, a Dew, that refreshes the Air, makes sickness to cease, and produces all those admirable effects, that make the Ægyptians wish for it so passionately. And the same spirits of Niter, being joyned to the Paste, and to the Mud, raise the one, and augment the weight of the other. That, which Mr. Buratini observes, that at the time of this inundation, the Niter-pits of the neighbouring places vomit out liquid Niter, and that one may see issue out of the Earth abundance of Chrystals of Nitre, is alledged to fortify this conjecture; Which is yet more confirm'd by the Fertility, communicated to the Earth by the Mud of this River. For, plants do grow there in such abundance, that they would choak one another, if it were not remedied by throwing Sand upon the Fields; insomuch that the Ægyptians must take as much pains to spread Sand to lessen the fatness of their Land, as other Nations do, to spread dung or other manure upon theirs to increase the fatnes.

In the Fourth and Fifth, the Author undertakes to prove, that all those strange effects cannot be attributed to Rain or Snow, and that the overflowing of the Nile always happens at a certain day.

In the Last, he alledges some Relations, serving to confirm his Opinion: which are too long here to insist upon.

DE PRINCIPIIS ET RATIOCINATIONE GEOMETRATUM; Contra Fastum Professorum Geometriæ; Authore Thoma Hobbes. It seems, that this Authour is angry with all Geometricians, but himself; yea he plainly saith in the dedication of his Book, that he invades the whole Nation of them; and unwilling, it seems, to be call'd to an account for doing so, He will acknowledge no judge of this Age, but is full of hopes, that posterity will pronounce for him. Mean while he ventures to advance this Dilemma; Eorum qui de iisdem rebus mecum aliquid ediderunt, aut solus insanio Ego, aut solus non insanio; tertium enim non est, nisi (quod dicet forte aliquis) insaniamus omnes. Doubtless, one of these will be granted him.

As to the Book it self, he professes, that he doth not write it against Geometry, but Geometers and that his design in it is, to shew, That there is no less uncertainty and falsity in the writings of Mathematicians, than there is in those of Naturalists, Moralists, &c. though he judges, that Physicks, Eticks, Politicks, if they were well demonstrated, would be as certain as the Mathematicks.

Attacking the Mathematical Principles as they are found in Books, and withall some Demonstrations, he takes to task Euclid himself, instead of all, as the Master of all Geometricians, and with him his best interpreter, Clavius, examining in the first place, the Principles of Euclid: Secondly, Declaring false, what is superstructed upon them, whether by Euclid or Clavius, or any Geometer whatsoever that hath made use of those or other (as he is pleased to entitle them) false Principles. Thirdly, Pretending, that he means so to combat all, both Principles and Demonstrations, undertaken by him, as that the will substitute better in their room, least he should seem to undermine the Science it-selfe.

The particulars, which he undertakes to reform, are,

Punctum. Radix & Latus.
Linea. Prop.16. El. 3.
Terminus. Dimensio Circuli.
Linea Recta. Magnitudo Circuli Hugeniana,
Superficies. Sectio Anguli.
Superficiei Termini. Ratio, quam habet recta composita ex Radio & Tangente 30. grad, ad Radium ipsum.
Angulus (Where he is large upon the Angulus Contactus.)
Petitio prima Elem. I. Euclidis. Propos. 47 &. Elem. 1. Demonstratio.
Ratio. Addita est Appendix de Mediis proprotionalibus in genere.

KING SALOMONS POURTRAITURE OF OLD AGE; by John Smith, M.D. This Treatise being a Philosophical Discourse, though upon a Sacred Theme, may certainly claim a place among Philosophical Transactions. Not here to mention the many other learned Notes, this Worthy Author gives upon that Hieroglyphical Description of Old Age, made by that Royal Pen-man of Ecclesiastes, cap. 12. We shall onely take notice of that surprisingly ingenious one, there to be met with, concerning the Antiquity of the Doctrine of the Blood's Circulation; King Salomon lived neer 2700 years agoe, using such expressions, as may, to a considering Reader, very probably denote the same Doctrine, which the Sagacious Dr. Harvey has of late years so happily brought to light, and introduced into all the most Ingenuous Societies of Learned men: The Pitcher, mention'd in the quoted place, being Interpreted for the Veines, and the Fountain, for the Right Ventricle of the Heart, as the Cistern, for the Left; the Wheele, there spoken off, manifestly importing a Circulation, made by the Great Artery with its Branches, the principal Instrument thereof.

Printed with Licence for John Martyn, and James Allestry, Printers to the Royal Society. 1666.