Philosophical Transactions/Volume 37/Number 417
VOL. XXXVII
PHILOSOPHICAL
TRANSACTIONS.
For the Months of January and February, 1731.
The CONTENTS.
351. ACER Fraxini foliis, serratis. Acer maximum; foliis trifidis & quinquefidis, Virginianum. Pluk. Phyt. Tab. 123. Fig. 4 & 5.
352.Agrimonia odorata. Cam. Hort.
353.Agrimonia officinarum. T. Inst. 301.
354.Agrimonia, minor; flore albo H. C. Boerh, Ind.
355.Anapodophyllon Canadense Morini. T. Inst. 239.
356.Apocynoides subhirsuta; floribus aurantiis.
357.Aracus, q. Vicia segetum; singularibus siliquis glabris. C. B. 345.
358.Brasica Orientalis, perfoliata; flore albo; filiqua quadrangular T. Cor. 16.
359.Brunella laciniata; flore elegantissimè sulphureo.
Boer. Ind. alt. 169.
360.Cassida Cretica; fruticosa; Catariæ folio;
flore albo. T. Cor. 11.
361.Cassida palustris, vulgatior; flore cæruleo.
T. Inst. 182.
362.Cassida orientalis; Chamædryos folio; flore luteo. T. Cor II.
363.Convolvulus Canariensis; longioribus foliis, mollibus & incanis. Pluk. Phyt. Tab, 325. Fig.I.
364.Daucus, quiPastinaca Œnanthes folio. Boccon. rar. 75.
365.Echinopus minor, annuus; magno capite, T. Inst. 463.
366.Frutex Afiicanus, Ambram spirans. Pluck. Phyt. Tab.183. Fig. I.
367.Galeopsis Hispanica; frutescens; Teucrii fo1io. T. Inst. 186.
368.Hedypnois annua. T. Inst 478.
369.Hedypnois Cretica, minor, annua. T. Cor. 36.
370.Hedypnois Hispanica, procumbens; magno capite. An Hedypnois annua, capite maximo. Boerh. Ind. alt. 93?
371.Heleniastrum; folio longiore & angustiore D. Vaillant. Acad. Reg. Par. anno 1720.
372.Heleniastrum feriùs florens; latiore folio; ramosissimum. An. Heleniastrum; folio breviore & latiore. Ejusdem Ibid?
373.Hieracium fruticosum, angustissimo, incano folio. H.L. Bat. 316.
374.Hieracium Pulmonaria dictum, latifolium, humilius; ramulis expansis.
375.Lamium Garganicum, subincanum; flore purpurascente, cum labio superiori crenato. Micheli. Hort.Pisan. 93. Tab. 32.
377. Lamium purpureum, perenne; foliis atutis, profundé incisis. Lamium; folio oblongo; flore rubro. Park. Theat. 606.
378. Lychnis Hispanica; folio Kali; multiflora. T. Init. 338.
379. Millefolium, vulgare, album. C. B. 140.
380. Millefolium album, incanum; segment is soliorum latioribus.
381. Millefolium nobile Tragi. 476.
382. Millefolium, odoratum, Monpeliense. Pillet. 271.
383. Millefolium, minus, tenuifolium; Tanaceti, odore. Barrel. Obs. No 1117.
384. Millefolium, tomenrosum, luteum. C. B. 140.
385. Millefolium; foliis Sophiæ fere divisura; floribus parvis, ex albo flavescentibus.
386. Mentha Sysymbrium dicta, hirsuta, rotundifolia; odore Aurantii D. Manningham. Mentha, Sifymbrium dicta, hirsuta; glomerulis & foliis minoribus ac rotundioribus. Raii Syn. Ed. 3. 233.
387. Myrrhis trifolia, Canadensis, Angelicæ facie. T. Inst. 315.
388. Pimpinella Sanguisorba major. C. B. 160.
389. Pimpinella major, rigida, prælta auriculata, Sabauda. Boccon. Mus. p. 19.
390. Ribes fructu parvo. Merret. Pin. Raii Syn. Ed. 3. 456.
391. Ribes Americana; fructu nigro minima; calyce floris campaniformi.
392. Sclarea; Africana; amplissimo folio; annua. Boerh. Ind. alt. 165.
393. Sideritis, Cretica, viscosa, Bitumen olens. Zanon. 186.
394. Veronica minor, Alpina, Serpylli folio. An Ponæ?
395. Virga aurea, Mexicana, C. B. 517. Virga aurea; Limonii folio; paniculâ uno versu disposita. H. Reg. Par.
396. Virga aurea, Americana, angustifolia, media; panicula speciosa.
397. Virga aurea Americana, altissima, angustifolia serotina; radice repente.
398. Virga aurea, humilis; foliis rigidis, latis, utringue acuminatis. An Virga aurea folio hirsuto, Salicis, raro & levissimè serrato; caulibus atropurpureis Boerh. Ind. alt. 97?
399. Virga aurea, montana; folio angusto, sub incano; flosculis conglobatis. Raii Syn. Ed. 2. 81.
409. Virga aurea minor; foliis serratis, utrinque acuminatis.
THE Wheels are placed under the Arches of London-Bridge, and moved by the common Stream of the Tide-Water of the River Thames.
A B the Axle-tree of the Water-Wheel, 19 Feet long, 3 Feet Diameter, in which C, D, E, F, are four Sets of Arms, eight in each Place, on which are fixed G G G G, four Rings, or Sets of Felloes, in Diameter 20 Feet, and the Floats H H H, 14 Feet long and 18 Inches deep, being about 26 in Number.
The Wheel lies with its two Gudgeons, or Centers, A B, upon two Brasses in the Pieces M N, which are two great Levers, whose Fulcrum, or Prop, is an arched Piece of Timber L, the Levers being made circular on their lower Sides to an Arch of the Radius M O, and kept in their Places by two arching Studs fixed in the Stock L, through two Mortises in the Lever M N.
The Wheel is, by these Levers, made to rise and fall with the Tide, which is performed in this Manner. The Levers M N are 16 Feet long; from M, the Fulcrum of the Lever, to O the Gudgeon of the Water-Wheel, 6 Feet; and from O to the Arch at N, 10 Feet. To the Bottom of the Arch N is fixed a strong triple Chain P, made after the Fashion of a Watch-Chain, but the Links arched to a Circle of one Foot Diameter, having Notches, or Teeth, to take hold of the Leaves of a Pinion of cast Iron Q, 10 Inches Diameter, with eight Teeth in it moving on an Axis. The other loose End of this Chain has a large Weight hanging at it, to help to counterpoise the Wheel, and preserve the Chain from sliding on the Pinion. On the same Axis is fixed a Cog-Wheel R, 6 Feet Diameter, with 48 Cogs. To this is applied a Trundle, or Pinion, S, of fix Rounds, or Teeth; and upon the same Axis is fixed T, a Cog-Wheel of 51 Cogs, into which the Trundle V, of six Rounds, works; on whose Axis is a Winch, or Windlass, W, by which one Man, with the two Windlasses, raises or lets down the Wheel as there is Occasion.
And because the Fulcra of these Levers, M N, are in the Axis of the Trundle K, viz, at M or X, in what Situation soever the Wheel is raised or let down, the Cog-Wheel II, is always equidistant from M, and works, or geers truly.
By Means of this Machine the Strength of an ordinary Man will raise about fifty Ton Weight.
I, I, is a Cog-Wheel fixed near the End of the great Axis, 8 Feet Diameter, and 44 Cogs working into a Trundle K, of 412 Foot Diameter, and 20 Rounds, whose Axis or Spindle is of Cast Iron 4 Inches in Diameter, lying in Brasses at each End, as at X.
Z Z is a quadruple Crank of Cast Iron, the Metal being 6 Inches square, each of the Necks being turned one Foot from the Center, which is fixed in Brasses at each End in two Head-stocks fastned down by Caps. One End of this Crank at Y is placed close abutting to the End of the Axle-tree X, where they are at those Ends six Inches Diameter, each having a Slit in the Ends, where an Iron Wedge is put, one half into the End X, the other half into Y, by Means of which the Axis X turns about the Crank Z Z.
The four Necks of the Crank have each an Iron Spear, or Rod, fixed at their upper Ends to the respective Libra, or Lever, a 1, 2, 3, 4, within three Foot of the End. These Levers are 24 Feet long, moving on Centers in the Frame b b b b; at the End of which, at c 1, 2, 3, 4, are jointed four Rods with their forcing Plugs working into d 1, 2, 3, 4, four Cast Iron Cylinders four Feet three quarters long, seven Inches Bore above, and nine below where the Valves lie, fastened by skrewed Flanches, over the four Holes of a hollow Trunk of Cast Iron, having four Valves in it just over e e e e, at the joining on of the Bottom of the Barrels, or Cylinders, and at one End a sucking Pipe and Grate f, going into the Water, which supplies all the four Cylinders alternately.
From the lower Part of the Cylinders d1, d2, d3, d4, come out Necks turning upward Arch-wise, as g g g g, whose upper Parts are cast with Flanches to skrew up to the Trunk h h h h; which Necks have Bores of 7 Inches Diameter, and Holes in the Trunk above communicating with them, at which Joining are placed four Valves. The Trunk is cast with four Bosses, or Protuberances, standing out against the Valves to give room for their opening and shutting; and on the upper Side are four Holes stopped with Plugs, to take out on Occasion, to cleanse the Valves. One End of this Trunk is stopped by a Plug i. To the other, Iron Pipes are joined, as i 2, by Flanches, through which the Water is forced up to any Height or Place required.
Besides these four Forcers, there are four more placed at the other Ends of the Libræ, or Levers (not shewn here to avoid Confusion, but to be seen on the left Hand) the Rods being fixed at a 1, 2, 3, 4, working in four such Cylinders, with their Parts d d, &c. e e, f, g g, and i, as before described, standing near k k.
At the other End of the Wheel (at B) is placed all the same Sort of Work as at the End A is described, viz.
| The Cog-Wheel | I. | The four Levers ac, ac, &c. |
| The Trundle | K. | 8 forcing Rods a d, a d, &c. |
| The Spindle | X. | 8 Cylinders d e, d e, &c. |
| The Crank | Y, Z. | 4 Trunks, such as e e, h h. |
| The sucking Pipes | f. | 2 forcing Pipes, as i. |
So that one single Wheel works 16 Pumps.
All which Work could not be drawn in one perspective View, without making it very much confused.
A Calculation of the Quantity of Water raised by
the Engines at London-Bridge.
 | A table should appear at this position in the text. See Help:Table for formatting instructions. |
In the 1st Arch next the City is one Wheel with double Work of 16 Forcers.
In the 3d Arch
1st Wheel double Work at one End, and single at the other 12
2d Wheel in the Middle 8
3d Wheel 16
In all 52 Forcers.
| A table should appear at this position in the text. See Help:Table for formatting instructions. |
One Revolution of a Wheel makes in every Forcer 2⅓ Strokes
So that one Turn of the 4 Wheels makes 114 Strokes.
When the River is at best, the Wheels go six times round in a Minute, and but 4½ at middle Water 6
The Number of Strokes in a Minute 684.
The Stroke is 2½ Feet, in a 7 Inch Bore, raises 3
Ale Gall.
They raise per Minute 2052
That is, 123120 Gallons = 1954 Hogseads per Hour, and at the Rate of 46896 Hogsheads in a Day, to the Height of 120 Feet.
This is the utmost Quantity they can raise, supposing there were no imperfections or Loss at all.
But it is certain from the Considerations following, that no Engine can raise so munch as will answer the Quantity of Water the Cylinder contains in the Length of the Forcer, or Piston's Motion: For,
First, The opening and shutting of the Valves lose nearly so much of that Column, as the Height they rise and fall.
Secondly, No Leather is strong enough for the Piston, but there must continually slip or squeeze by some Water, when it is raised to a great Height; and when the Column is short, it will not press the Leather enough to the Cylinder, or Barrel; But especially at the Beginning, or first moving of the Piston, there is so little Weight on it, that before the Leather can expand, there is some Loss.
Thirdly, And this Loss is more or less, as the Pistons are looser or straighter leathered.
Fourthly, When the Leathers grow too soft, they are not capable of sustaining the Pillar to be raised.
Fifthly, If they are leathered very tight, as to lose no Water, then a great Part of the Engine's Force is destroyed by the Friction.
By some Experiments I have accurately made, on Engines whose Parts are large and excellently performed, they will lose (illegible text) and sometimes ¼ of the calculated Quantity.
However, the Perfections or Errors of Engines are to be compared together, by the calculated Quantities or Forces; for as they differ in those, they will proportionably differ in their actual Performances.
The Power by which the Wheels are moved.
The Weight of the Pillar. of Water on a Forcer 7 Inches Diameter, and 120 Foot high.
7 x 7 = 49lb The Pounds Averdupoise in a Yard nearly.
40 Yards high.
1960 lb on one Forcer.
8 Forcers always lifting.
The whole Weight 1568lb = 140Ct. = 7 TunWeight on the Engine at once.
Then the Crank pulls the Libra 3 Feet from the Forcer, and 8,3 Feet from the Center,
7 Tun
× 11.3
8,3)79.1 (9,5 Tun on the Crank. Tun.
Wallower 2,2)9,5(4.3 on Trundle;
The Spur Wheel 4
The Radius of the great Wheel 10) 17,2 1,72 Tun.
20
The Force on the Floats 18 Ct. 40 lb 34,40 Ct.
But to allow for Friction and Velocity, may be reckoned 1 Tun ½.
The Ladles or Paddles 14 Foot long, 18 Inches deep, --
= 22,4 square Feet.
The Fall of Water is sometimes
2 Feet.
44,8
6 Gall. in a Cub. ft.
)268,8
10, lb a Gallon.
112)2688.(24 Hundred.
The Velocity of the Water, 4 Feet in 21″′ of Time.
21″′ — 4 Ft. :: — 60″: = 685 Feet per Minute.
The Velocity of the Wheel = 310 Feet per Minute.
Quantity expended on the Wheel, according to the Velocity of the Stream 1433 Hogsheads per Second.
But at the Velocity of the Wheel 645 Hogsheads per Second.
The Velocity of the Wheel to the Velocity of the Water, as 1 to 22.
Some Observations on these Water-Works.
Although they may justly be esteemed as good as any in Europe, yet are there, as I conceive, some Things which might be altered very much for the better.
First, If instead of sixteen Forcers they worked only eight, the Stroke might be five Feet in each Forcer, which would draw a great deal more Water with the same Power on the Wheel; for then there would be but half the opening and shutting of Valves, consequently but half that Loss: And a five Foot Stroke draws above double the Quantity of two Strokes of 2½ each, by near ⅓, in regard the Velocity is double, which is the most valuable Consideration in an Engine, where the Pipes will sustain such Force.
Secondly, The Bores that cart off the Water from the Forcers are too small, there being (nearly) always two Pillars of 7 Inches Diameter, forcing into one Pipe of the same Diameter, and 7 x 7 = 49 + 49 = 98.
Therefore those Pipes of Conveyance should be near nine Inches Diameter.
The Perfections of the Machine.
The Timber-work is all admirably well performed, and the Composition and Contrivance, for Strength and Usefulness, not exceeded by any I have seen.
The cast Iron Cranks are better than wrought ones, by reason they are very stiff, and will not be strained, but sooner break; but then they are cheap, and new ones easily put in.
The Wedge for putting on or releasing the Crank and Forcers, is better than the sliding Sockets commonly used.
The forcing Barrels, Trunks, and all their Apparatus, are very curiously contrived for putting together, mending, altering or cleansing, and subject to as little Friction as possible in that Part.
The Machine for raising and falling the Wheels is very good, though but seldom used, as they tell me; for they will go at almost any Depth of Water, and as the Tide turns, the Wheels go the same Way with it.
These Machines at London-Bridge are far superior to those so much famed at Marly in France, in regard the latter are very ill designed in their Cranks, and some other Parts.
CUM nuper, Vir Præstantissime, qualemcunque apparatum meum & Anatomicum & Chirurgicum & Botanicum, aliasque res & naturales & præter-naturales inspicere dignatus sis, atque inter alia Calculos Vesicæ in homine vivo in vesica sponte fractos, & per urethram feliciter excretos Tibi demonstraverim, simulque monuerim, hoc quam rarissime contingere, & propterea solutionem calculi in vesica a quam plurimis, atque cum primis etiam ab Anglis recensioribus impossibilem haberi pronunciarique, rogasti, ut Tibi propediem in Angliam redeunti, frustula nonuulla horum calculorum cum brevi quadam historia sive descriptione darem, quæ Academiæ Regiæ Londingnsi, cujus membrum es dignissimum, offerres, ut Ipsa insolitam atque inusitatam hanc rem videre, ultefiorique scrutinio subjicere, imo & incredulous rem ita vere actam esse persuadere possit. Quare cum præcipue id mihi negotii datum esse existimem, ut verum in unaquaque re pateat, atque scientiæ artesque liberales hoc ipso melius perficiantur atque augeantur, mitto Tibi hac occasion nonnulla ehorum calculorum frustula, cum brevi & vera actæ rei historia.
Est nimirum his in terris Brunsvicensibus in Cœnobio seculari, quad Marienthal appellatur, & ad horæ circiter distantiam ab Helmstadio, celebri Academiæ Juliæ sede, situm est, rerum œconomicarum hujus Cœnobii Præfectus, nomine Widmannus, Vir sexagenario major, sed robustus & durc vitæ victusque generi adsuetus, qui per plures annos primo calculo renum sæpe & vehementer laboravit, eotumque sensim magnam copiam, quorum multi Pisi magnitudinem superarunt, per iter urinæ haud sine magnis doloribus excrevit. Tandem veto quatuor ab hinc annis calculi quoque vesicæ omnia percepit symptomata, ita, ut sæpe non nisi maximis cruciatibus in pubis & perinæi regione perceptis urinam excernere voluerit. Tandem vero anno 1728, poftquam aliquamdiu variis, ut fieri his in casibus solet, usus erat remediis, & inprimis Tintura antinephritica, ut vocant Lipsiensi sive Rothiana, atque simul cerevisiam illam his in regionibus contra calculum celeberrimam, quæ Regiæ Luteræ vulgo Konigs-Lutter, oppido Brunsvicensi, coquitur, & quam Duchstein appellant, hancque ob causam in loca sive urbes remotissimas devehitur, continuo pro potu ordinario hauserat, aliquando vehementes inter mingendum dolores, nisum & constrictionem in vesica, sensunque eo ipso, ac si calculus, sive calculi in vesica frangerentur ac dissilirent, percepit, eoque ipso mox aliquot frustula calculi fracti cum lotio dejecit, quæ deinde per plutes dies alia secuta sunt, donec tandem ab eis liberates bene atque pancratíce ab omnibus & calculis & calculi doloribus, immunis nunc vivat. Calculos plures una in hoc viro fuisse Page:Philosophical Transactions - Volume 037.djvu/21 camentorum, an cerevisæ illius, an naturæ benefic io disrupti & expulsi sint. Ex segmentis frustulorum valde convexis, quæ hic mitto, & quæ adhuc adservo, judicare licet, vix ullum illorum calculorum nucem moschatam superasse, plures vero minores fuisse. Interea tamen solutionem calculorum in vesica haud prorsus impossibilem esse, mihi evincere videntur, licet res forte quam rarissime contingat. Vale mihique save.
Dab. Helmstadii in Amcademia Julia ipsis Calendis Octobris, m dcc xxx.
THE late Frost having been almost as intense as any that hath been for many Years, I send you my Account of it; which if you think Worth the Cognizance of the Royal Society, be pleased to impart it to them.
In the Philosophical Transactions for November and December, 1709, Numb. 324, I have given an Account of some of the most remarkable Frosts that I could find any Relation of; and particularly of that great and, I had almost said, universal one in 1708, which the Society had very good Histories of from divers Parts, and which, in that Transaction, I have given an Account of from the Original Papers, which Page:Philosophical Transactions - Volume 037.djvu/23 Page:Philosophical Transactions - Volume 037.djvu/24 Page:Philosophical Transactions - Volume 037.djvu/25 Page:Philosophical Transactions - Volume 037.djvu/26 repeating its Attractions and Repulsions for many Times together: I then fixed the Ball on longer Sticks, first upon one of eight Inches, and afterwards upon one of twenty-four Inches long, and found the Effect the same. Then I made use of first Iron, and then Brass Wire, to fix the Ball on, inserting the other End of the Wire in the Cork, as before, and found that the Attraction was the same as when the Fir-Sticks were made use of, and that when the Feather was held over against any Part of the Wire, it was attracted by it; but though it was then nearer the Tube, yet its Attraction was not so strong as that of the Ball. When the Wire of two or three Feet long was used, its Vibrations, caused by rubbing the Tube, made it somewhat troublesome to be managed: This put me upon thinking, whether if the Ball was hung by a Packthread, and suspended by a Loop on the Tube, the Electricity would not be carried down the Line to the Ball: I found it to succeed accordingly; for upon suspending the Ball on the Tube by a Packthread about three Feet long, when the Tube had been excited by rubbing, the Ivory Ball attracted and repelled the Leaf-Brass, over which it was held, as freely as it had done, when it was suspended on Sticks, or Wire; as did also a Ball of Cork, and another of Lead that weighed one Pound and a quarter.
After I had found that the several Bodies above mentioned had an Electricity communicated to them, I then went on to see upon what other Bodies the Tube would have the same Effect, beginning with the Metals, suspending them on the Tube by the Method above mentioned; first in small Pieces, as with a Guinea, a Shilling, a Half-penny, a Piece of Block-Tin, a Piece of Lead; then with larger Quantities of Metal, suspending them on the Tube by Packthread. Here I made use of a Fire-Shovel, Tongs, and Iron Poker, a Copper Tea-Kettle, which succeeded the same, whether empty, or full of either cold or hot Water; a Silver Pint Pot; all which were strongly Electrical, attracting the Leaf-Brass to the Hight of several Inches. After I had found that the Metals were thus Electrical, I went on to make Trials on other Bodies, as Flint-Stone, Sand-Stone, Load-Stone, Bricks, Tiles, Chalk; and then on several vegetable Substances, as well green as dry, and found that they had all of them an Electrick Vertue communicated to them, either by being suspended on the Tube by a Line, or fixed on the End of it by the Method above mentioned.
I next proceeded to try at what greater Distances the Electrick Vertue might be carried, and having by me Part of a hollow walking Cane, which I suppose was Part of a Fishing-Rod, two Feet seven Inches long; I cut the great End of it, to fit it into the Bore of the Tube, into which it went about five Inches; then when the Cane was put into the End of the Tube, and this excited, the Cane drew the Leaf-Brass to the Hight of more than two Inches, as did also the Ivory Ball, when by a Cork and Stick it had been fixed to the End of the Cane. A solid Cane had the same Effect, when inferred in the Tube after the same Manner as the hollow one had been. I then took the two upper Joints of a large Fishing-Rod, the one of Spanish Cane, the other partly Wood and the upper End Whale-bone, which, together with the Tube, made a Length of more than fourteen Feet. Upon the lesser End of the Whale-bone was fixed a Ball of Cork of about an Inch and quarter Diameter; then the great End of the Rod being inferred in the Tube, the Leaf-Brass laid on the Table, and the Tube excited, the Ball attracted the Leaf-Brass to the Hight of about three Inches by Estimation. With several Pieces of Spanish Cane and Fir-Sticks I afterwards made a Rod, which, together with the Tube, was somewhat more than eighteen Feet long, which was the greatest Length I could conveniently use in my Chamber, and found the Attraction very nearly, if not altogether as strong, as when the Ball was placed on shorter Rods. Thus far I proceeded before I went into the Country, which I did the 2d of May, 1729, taking with me several Glass Canes, and such other Materials I thought would be necessary, and could not well be procured there. I shall now give an Account of the Experiments I then made, some of which were made at Norton-Court near Feversham in Kent, at my honoured Friend's John Godfrey's, Esq; the other at Otterden-Place, at my honoured Friend's Granvil Wheler's, Esq; a worthy Member of the Royal Society, with whom I have had the Honour to be lately acquainted. I shall set down each Experiment in the Order of the Time and Place they were made, as I find it in my Notes.
The first Experiment was made at Norton-Court, May 14th, 1729, between six and seven o'Clock in the Evening. Having provided a Rod of about twenty-four Feet, that consisted of a Fir-Pole, of Cane, and the Top of Reed, upon the End of which the Ball of Cork was placed, and the great End of the Rod put into the Tube about seven or eight Inches; then the Page:Philosophical Transactions - Volume 037.djvu/30 Page:Philosophical Transactions - Volume 037.djvu/31 Page:Philosophical Transactions - Volume 037.djvu/32 Page:Philosophical Transactions - Volume 037.djvu/33 Page:Philosophical Transactions - Volume 037.djvu/34 Page:Philosophical Transactions - Volume 037.djvu/35 Page:Philosophical Transactions - Volume 037.djvu/36 himself, that might see there was an Attraction; which I saw, though I perceived it not to be so strong, as when the Attraction was carried by a longer Line, by returning it, as in the Experiments above-mentioned. The Length of the Line was 650 Feet. This was several Times repeated, but the Experiment being made in the Evening, at length the Dew began to fall. We began about Seven o'Clock, or some little Time after, but before Eight the Attraction ceased: But whether this was caused by the Dew falling, or by my being very hot, we-could not positively say, but I rather impute it to the latter. This Experiment was made July 14, 1729.
Note, That though we call the carrying the Electrick Vertue by the Lines in this Position Horizontal, you are not to understand it in a strict Sense, as may be easily perceived by the Description of the Method; and That as the Line swagged down much below the Silk Lines that supported it, in the middle Part between those Lines, it was some Feet longer than the Distance of the Poles.
Some Days after this Experiment was repeated from the Turret Closet Window, when the Line was 765 Feet, and the Attraction was no less perceivable than in the Experiment above-mentioned.
A large Map of the World, that had twenty-seven square Feet in it; a Table-Cloth containing fifty nine square Feet; these suspended on the Tube by Page:Philosophical Transactions - Volume 037.djvu/38 Page:Philosophical Transactions - Volume 037.djvu/39 Page:Philosophical Transactions - Volume 037.djvu/40 Page:Philosophical Transactions - Volume 037.djvu/41 Page:Philosophical Transactions - Volume 037.djvu/42 Page:Philosophical Transactions - Volume 037.djvu/43 Page:Philosophical Transactions - Volume 037.djvu/44 Page:Philosophical Transactions - Volume 037.djvu/45 under his Thighs: Then the Leaf-Brass was laid on a Stand, which was a round Board of a Foot Diameter, with white Paper passed on it, supported on a Pedestal of a Foot in Hight, which I often made use of in other Experiments, though not till now mentioned: Upon the Tube's being rubbed, and held near his Feet, without touching them, the Leaf-Brass was attracted by the Boy's Face with much Vigour, so as to rise to the Hight of eight, and sometimes ten Inches. I put a great many Pieces on the Board together, and almost all of them, came up together at the same Time. Then the Boy was laid with his Face upwards, and the hind Part of his Head, which had short Hair on, attracted, but not at quite so great a Hight as his Face did. Then the Leaf-Brass was placed under his Feet, his Shoes and Stockings being on, and the Tube held near his Head, his Feet attracted, but not altogether at so great a Hight as his Head: Then the Leaf-Brass was again laid under his Head, and the Tube held over it, but there was then no Attraction, nor was there any when the Leaf-Brass was laid under his Feet, and the Tube held over them.
April the 16th, I repeated the Experiment with the Boy, but now the Attraction was not quite so strong as at the first, the Brass not rising higher than to about six Inches. His Hands being stretched nearly horizontal, I placed a small Stand with Leaf-Brass under each Hand, and under his Face the great one, furnished as the others, when the excited Tube being held near his Feet, there was an Attraction by his Hands and Face at the same Time. I then gave him the Top of a Fishing-Rod to, hold in his Hand; there was a Ball of Cork stuck on the little End of it, under which the Leaf-Brass, being laid; and the Tube rubbed and held near his Feet, the Ball attracted the Leaf-Brass to the Hight of two Inches, and repelled it, and attracted for several Times together with great Vigour.
April 21, I again repeated the Experiment on the Boy; and now he attracted much stronger than at the first: The Leaf-Brass rose to his Face at the Hight of more than twelve Inches. Then I gave the Boy to hold in each Hand the Tops, of two Fishing-Rods, with a Ball of Cork on each of their lesser Ends; then a small Stand being set under each Ball, with the Leaf-Brass on it, the Tube being rubbed, and held near his Feet, both the Corks attracted and repelled together strongly. The Length of the Poles were each of them about seven Feet. Then the Boy was laid on his left Side, and a Fishing-Rod, of near twelve Feet in Length, given him to hold with both his Hands; there was a small Ball of Cork at the Ends of the Rod, that was an Inch and three quarters Diameter: Then all Things being prepared, the Tube held hear the Boy's Feet, the Cork Ball attracted and repelled the Leaf-Brass with Force to the Hight of at least two Inches.
Note, That when I speak of holding the Tube near the Boy's Feet, I mean over against the Soles of his Feet; and when near his Head, is to be understood the Crown of his Head; for when the Tube is held above, or over his Legs, the Attraction is not so strongly communicated to the other Parts of his Body.
Page:Philosophical Transactions - Volume 037.djvu/48 Page:Philosophical Transactions - Volume 037.djvu/49 Page:Philosophical Transactions - Volume 037.djvu/50 Page:Philosophical Transactions - Volume 037.djvu/51 Page:Philosophical Transactions - Volume 037.djvu/52 Hæc de hujus doctrinæ fontibus indigitasse, non abs re fore judicatum est, ne, lectoribus inexercitatis, auctoris nimia brevitas impedimento esset.
Propositio.
In circumferentia circuli (Tab. 2. Fig. 1.) centro quovis O intervallo O R = a descripta applicetur chorda R T = b, cui parallelus ducatur radius O P, ita quidem ut arcus P R sit quadrante major si habeatur + b, minor vero si habeatur − b. Incipiendo in puncto R, sumantur ordine tot arcus , &c. arcui P R æquales, quot unitates continet fractio , & a punctis &c. ducantur totidem rectæ , &c. radio O P parallelæ & rectæ O R occurrentes in punctis, , &c. Deinde dividatur arcus P R in tot partes æquales quot sunt unitates in numero n, quarem illa quæ puncto P Page:Philosophical Transactions - Volume 037.djvu/54 Page:Philosophical Transactions - Volume 037.djvu/55 Page:Philosophical Transactions - Volume 037.djvu/56 obiit. Fœminam adhuc viventem vidit non tantum, & hac figura ad vivum depingere curavit, sed ipsam Plicam post obitum resectam secum Wittebergam attulit Clariss. D. Flouricke dicti Principis Medicus. Erat autem Plica (quatuor ulnas longa, palmum lata, duosque pollices crassa, sed altero tanto longior foret, ipso referente, nisi magna ejus pars, temporis quo ægra decubuit diuturnitate, squalore & attritu consumpta fuisset. Hunc ergo Casum penitus extraordinarium, illustrissimæ Societati Regali exponere volui. Spero autem fore, ut imposterum de circumstantiis singularibus hujus casus a laudato Viro certior reddar, quas alio tempore communicabo.
SIR, January 20th, 1730/1.
* * *THE Plica has been always related, and thought to be a Distemper, and to proceed from a Fever or Convulsions; but for my Part, from the best Information I could get concerning it, I 
"The great Multitude of People in Poland, who are troubled with this Plica, first made me reflect, whether it were a real Disease or no? I am now convinced, that their swinish Way of living, and the common Opinion so deeply rooted in the Generality of People, that this Lock of Hair cannot be taken off without Danger of their Lives, have contributed more to this Complaint than any real Indisposition of Body; considering that it is the middling or poor People, who are troubled with it; whom then one cannot look on without Horror: But no German, of whom there are great Numbers, who live in that Country, ever had any such thing grow. Many of them, who are married to Women of Polish Birth, are scarce able to perswade their Wives not to train up their Children to this Nastiness. Not long since I saw a Fellow in the Church, who had about seventy of such Locks hanging down from his Head, which "were as hard twisted, as so many Penny Cords; that one might easily have taken his for a Medusa's Head (and who knows, but that in ancient Times some such Locks as these might have given Rise to the Poetical Fiction of Snakes growing on the Head instead of Hair? Be that as it will, this is certain, it is a most odious Sight to look on."
ON the second of September, 1724, a little after Noon, being in Latitude 41° 10' N. and Difference of Longitude from Cape Henry in Virginia about 28° 00' E. the Weather fair, a moderate Gale, and smooth Sea, my Mate, who was on the Deck, came and told me, that the Compass traversed so much that he could not possibly steer by it: Whereupon I went up, and after trying it in several Parts of the Ship, found what he said to be true. I then had all my Compasses brought up, and placed in different Parts of the Ship, and in Places most remote from Iron, and, to my great Surprize, found them all in the same Condition; so that we could not steer by any of them. I then new touched some of them with a Loadstone, which I always carry with me; and left that should affect them, sent it out to the End of the Bowspreet; but I did not perccive that the new touching was of any Service, for they all continued traversing very swiftly, for about an Hour after I came on the Deck, and then on a sudden every one of them stood as well as usual. During the whole Time, the Ship had very little Motion; and I had an Azimuth Compass, and four or five others.
FINIS.
ERRATA which have escaped Notice till now.
NUMB. 415. p.378. l. 5. for majore read minore. Numb. 416. p.444. l. 8. from the Bottom,for dead read down. Ibid. l. 7. for ghostly read gastly.