Popular Science Monthly/Volume 20/April 1882/Popular Miscellany

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Popular Science Monthly Volume 20 April 1882  (1882) 
Popular Miscellany


About Eggs.—All eggs of birds are good for food, and all are palatable enough to be eaten by a hungry man; but the most and the best food-eggs are furnished by the gallinaceous birds. The number of eggs consumed in the more populous countries is immense. Great Britain imports 785,000,000 from the Continent, they representing a value of more than £2,500,000; while Ireland furnishes nearly 500,000,000; and the home production is probably nearly equal to the amount of the importation from the Continent. The consumption, already so large, is increasing at a rate which shows that the value of this kind of food is steadily and rapidly growing in appreciation. The United States is supposed to produce 9,000,000,000 eggs annually, of which 25,500,000 dozen are sent to the New-York market. More than 800 dozen eggs are consumed in a single English hospital in the course of a year. The use of eggs as a standard article of diet has been limited by reason of their perishable nature; but this difficulty is now, in a measure, obviated by the desiccating and condensing process practiced in St. Louis and New York, and the canning process of Herr von Effner in Germany. Eggs are preserved in some parts of England by boiling them, removing the shells, and pickling them; in the United 856


��States, by the common liming process, which keeps them fit for every purpose except that of boiling ; and in China, by covering them with a paste of lime, salt, and ashes, from which they come out, however, rather the worse in appearance and smell. All eggs brought to Paris must be examined before being offered for sale ; and sorted, by being passed through rings of three centimetres eight millimetres in diameter for the small, and four centimetres for the average size. An ordinary fowl's egg weighs from one and a half to two ounces ; the egg of the duck from two to three ounces ; those of the sea- gull and turkey from three to four ounces ; that of the goose from four to six ounces. Eggs of wild birds are esteemed on account of the flavor that is given them by the food of the birds, and on account of the larger proportion of the more nutritious yellow that they contain. The ostrich is beginning to take rank as a valuable egg-producing domestic fowl. Each female bird will lay from twelve to sixteen, even, according to some, from twenty-five to thirty eggs, in August and September; and, as several couples will sometimes unite to hatch to- gether, it often happens that as many as sixty eggs may be found in and around a single nest. Each of these eggs is consid- ered equivalent to twenty-four eggs of the domestic hen ; so that, as single domesticated birds have been said to lay eighty-two eggs in a season, we have the possible product of one ostrich represented by 2,624 hens' eggs. The eggs of the Australian emu, which are nearly as large as those of the ostrich, and green, are eaten by the settlers with much relish, although they are some- what strong in flavor. The eggs of the Rhea ostrich of the South American pam- pas, of which forty, fifty, or seventy may be found in a nest, form a staple article of food during the spring months. The eggs of sea- fowl are largely consumed in many places, and those of the gull give rise to a consid- erable trade. A business of this kind is ac- tively carried on off the coast of Northum- berland, where prodigious quantities of eggs are collected ; at the Pedro Keys, near Ja- maica, where several kinds of sea and land birds resort ; the coasts of Norway and Lab- rador ; Funk bland, near Newfoundland ; parts of the African coast, and islands gen-

��erally. Eggs of water-fowl form an impor- tant part of the food of the Faroe Islands ; the eggs of the dusky petrel are sent, in immense quantities, from Bass's Strait to Tasmania and Australia ; incredible num- bers of auks' eggs are collected on the coast of Labrador ; the eggs of the rnalee- bird of Celebes are esteemed a great deli- cacy, and will each fill an ordinary tin cup, and form, with bread or rice, a very good meal.

The Yellows in the Peach-Tree. Mr.

W. K. Iligley has given in the " American Naturalist " an account of the observations he has made to learn the cause of the yel- lows in the peach-tree and the manner in which it is disseminated. He is satisfied that the disease is due to a fungoid growth, but not to a noemaspora, as ilr. Taylor, of the Agricultural Department at Washing- ton, believes, for that form occurs on other trees that receive no harm from its pres- ence ; nor to a fungus in the tissues of the roots, for no fungus has been recorded as occurring there. He worked, in his exam- inations, upon the theory that the fungus must be natural to the tree, enjoying the same conditions of development as are fa- vorable to the growth of the tree. Hence, he took no pains to cultivate the plant, but examined specimens as they were gathered from diseased trees. Nothing was found in the roots. Mycelia were found in sections of the trunk, on the under side of the inner bark next to the cambium layer, with many of the filaments penetrating and ramifying through that layer, and, in some specimens, mycelia between the layers of wood. In some of the smaller branches and the grow- ing ends of the larger branches, the tissues seemed to be completely filled with mycelia, and in one case the bark appeared to be split. Filaments of fungus were found in the leaves of the abnormal branches char- acteristic of trees affected with the yellows, and the chlorophyl in all such leaves was completely disorganized. The most satis- factory results were obtained from the ex- amination of the fruits, in which mycelia were abundantly found just beneath the skin, extending for a short distance into the fleshy parenchyma. The form was the same as that which was found in other parts



��of the tree ; this form, Mr. Higlcy believes, as the final result of his investigations so far, to be at least a part of and probably the whole cause of the disease. The affec- tion is, of course, transmitted by whatever will convey the fungus or its spores. Mr. Higley has no faith in any of the cures that have been proposed for the yellows, and be- lieves that where they have seemed to be successful, not yellows, but some other cause of trouble was present. The only remedy he can propose is to root out the tree and burn every part.

The Approaching Transit of Venns.

An international conference respecting the observations of the transit of Venus, which will take place next December, was held in Paris last October, under the presidency of M. J. B. Dumas. Most of the European countries, Brazil, Chili, and the Argentine Republic, were represented, and reported upon the observing stations which would be cared for by their respective countries. France will establish eight stations, Brazil five, Germany four, Denmark and the Neth- erlands, Austria, Hungary, Chili, and Mexico one each, Spain and the Argentine Repub- lic two each, forming a line of stations from the southern part of the United States through Central America, the West Indies, and the east and west coasts of South America to the Strait of Magellan. Besides these, Great Britain will have sixteen sta- tions arranged in groups of two, with prin- cipal centers of observation at the Cape of Good Hope, in Australia, New Zealand, and the Antilles ; and Portugal will have two stations within its proper limits, and one at Benguela or Lorenco Marquez. No reports were made from Italy and the United States. A committee to which the subject was re- ferred made a report concerning the best arrangements for details of observation ; and a resolution was adopted in favor of calling, after the return of the observing expeditions, an " International Commission on the Transits of Venus," in which each state should be represented by a plenipo- tentiary, to form a provisional organization for collecting all the data of the observa- tions, and deducing from them in common a general determination of the parallax of the sun.

��Sewage in Oysters. The oysters of Dublin Bay arc threatened with extinction in consequence of the turning of the sewage of the city into the water. Edible fish were numerous a generation ago in the river Lif- fey, which is the chief carrier of sewage to the bay, but now they are rarely seen there. Oysters were taken for examination, by Dr. Charles A. Cameron, from a spot which is covered by about ten feet of water at high tide, but is nearly dry at low water. The brine of a large proportion of them emitted a slight but distinctly fetid odor, and when examined microscopically was found to swarm with micrococci and other low organ- isms of sewage. Of samples of sea-water taken at the beds at high tide and from little pools containing oysters at low water, the latter contained ten times as much al- buminoid ammonia and thirty times as much saline ammonia as the former, prov- ing that it was in great part composed of sewage. It is impossible for the oysters to keep from imbibing much of this water ; and if we sometimes acquire the germs of fever from drinking water and milk, why may we not also from the juice of oysters raised in sewage-polluted waters ?

Malarial Organisms. M. A. Laveran has found, in the blood of patients suffering from malarial poisoning, parasitic organ- isms, very definite in form and most re- markable in character; motionless, cylin- drical curved bodies, transparent and of delicate outlines, curved at the extremities ; transparent spherical forms provided with fine filaments in rapid movement, which he believes to be animalcules; and spherical or irregular bodies, which appeared to be the " cadaveric " stage of these, all marked with pigment-granules. He has also detect- ed peculiar conditions in the blood itself. During the year that has passed since he first discovered these elements, M. Lave- ran has examined the blood in one hundred and ninety-two patients affected with vari- ous symptoms of malarial disease, and has found the organisms in one hundred and eighty of them, and he has convinced him- self by numerous and repeated observations that they are not found in the blood of persons suffering from diseases that are not of malarial origin. In general, the

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��parasitic bodies were found in the blood only at certain times, a little before and at the moment of the accession of the fever ; and they rapidly disappeared under the in- fluence of a quinine treatment. The ad- dition of a minute quantity of a dilute solution of sulphate of quinine to a drop of blood sufficed to destroy the organisms. Mr. Laverau believes that the absence of the organisms in most of the cases (only twelve in the whole one hundred and ninety- two) in which he failed to find them was due to the patients having undergone a course of treatment with quinine.

The Freezing of a Salt Lake. Dr. Wo-

eikoff has published the results of some observations which were made at his sug- gestion into the conditions of freezing and thawing of a salt lake near Orenburg, Russia. The lake has a surface of 473 square metres and is about five feet deep. Its water contains sixteen per cent of salt, and the mud of its bottom is rich in sul- phuretted hydrogen. During January, 1S79, except for one day, when the temperature was barely above the freezing-point, the thermometer in the air ranged from 6*3 to 28 - 2 centigrade, while the tempera- ture of the water at the surface was from 3-4 to 13 C, and at the bottom from -3-8 to 12-8 C. On the 27th of De- cember, when the temperature of the air was as low as 21 C, the lake was covered with a viscous ice, which soon began to thaw, however, when the temperature of the air rose to 6 C, and the temperature of the water was as low as 7"8 C. By the 3d of January all the ice had disappeared, but the temperature of the water was still 7'2 C. below the freezing-point, or about 19Fahr. On January 11th, the temperature of the air being 22 C, and that of the water being 9*8 C. at the surface and 5'6 at the bottom, the lake began again to be covered with viscous ice, and soon froze, the ice reaching a thickness of about six inches in ten days. But the remainder of the water was still unfrozen, notwithstand- ing that its temperature decreased to 10 C. on January 1 7th, and even to 12 - 8 C. on January 30th. Never before, says Dr. Wocikoff, were temperatures below 4 C. or 24"8 Fahr. observed in saline solutions

��outside of laboratories, while here were temperatures of 13 C, or 8'6 Fahr., observed in a salt lake. However, former experiments, especially those of M. Zop- piitz, have proved that there is no diffusion of salt before congelation ; it seems that in this lake (Kupalnoze) there is such a diffu- sion of salt toward the lower stratum of water, even before the freezing begins, oth- erwise it would be difficult to explain how colder water might remain on the surface, were it not for the greater amount of salt in the lower strata. It has always' been difficult to explain how ice is formed on the surface of oceans while the temperature of maximum density is lower than that of con- gelation, and the observations on this lake were instituted in the hope that they might throw light upon the subject. The lake, however, contains too much salt to afford a sure standard of comparison with oceanic water.

A Collection of Quaint Scientific Instru- ments. The Royal Mathematical and Phys- ical Museum, in Dresden, Saxony, was founded by Prince Augustus I in the six- teenth century, and has grown into an ex- tensive collection of articles illustrating the condition of science at particular periods, and its progress. " According to Adam Ries," a German expression to denote that any fact is mathematically exact, refers to the mathematician, Adam Ries, who in 1550 published a little book on reckoning with counters and with the Arabic numerals. His counters, and the hand-circles, staffs, and various devices with which people made their calculations before the Arabic numerals came into general use, are shown here. Another curious instrument, of the eighteenth cen- tury, is a proportion staff " for the mechan- ical extraction of the square and cube roots, and the proportioning and calculation of geometrical figuies." Among the optical instruments is the famous burning mirror of Walter von Tschirnhausen, of which the "Acta Erudita " from 1687 to 1C97 says, " He has with this glass set fire to wet wood in an instant, boiled water in a small ves- sel, melted lead, bored through iron plates, changed brick and stone to glass." Tschirn- hausen performed the first experiments on solubility of the earths with this instrument.



��The collection of clocks comprises nearly every conceivable variety of time-pieces, from sand-clocks to the Dresden Universal Clock which gave the time at three hundred and sixty places, and automatons driven by clock-work. The collection of telescopes covers nearly the whole history of the in- strument, beginning with a Galileo's tele- scope and including a Kepler's, a Rheita's, the Huygens's, Dolland's, and Frauenho- fer's refractors, and several kinds of re- flectors. One of the most precious articles in the collection is a very elaborate globe, with all the principal constellations and as- tronomical lines, and the magnitudes of the stars carefully indicated, which bears an inscription stating that it was made by Mohammed Ben Muwajed-el-Ardhi, without date or place of making. Beigel, of Dres- den, calculated in 1808, from the positions of some of the stars on the globe, that it must have been made in the ninth century. Dr. Adolph Drechsler believes that the maker was a son of the famous astronomer Muwajcd, who was called by Hulagu, the third emperor of the Mogul dynasty, from Damascus to superintend the observatory at Maragha, and that the date of the instru- ment was about a. d. 1279. The chief val- ue of the collection is in the opportunities it affords for the study of the development of instruments in the several branches of science.

Evolution of Deer-Horns. Mr. W.

Boyd Daw-kins has called attention to the confirmation of the doctrine of evolution afforded by the development of the an- tlers of animals of the deer-kind. In the middle stage of the Miocene, the cervine antler consists merely of a forked crown. This increases in size in the Upper Miocene, though it still remains small and erect, being not quite eleven and a half inches long, with four small tines in Ccrvus Matheri. The antlers of the succeeding (Pliocene) deer, in the Auvergne, were longer and larger and more branching than those of any earlier deer, and had three or more well-developed tines. The Ccrvus dicranios of the Upper Pliocene of the Val d'Arno had antlers so complicated as almost to defy description, though they were still smaller than those of the Irish elk. That

��animal survived into the succeeding age, and has been described in England as Sedg- wick's deer. The Irish elk, moose, stag, reindeer, and fallow deer, appeared in Eu- rope in the Pleistocene age, all with highly complicated antlers in the adult, the first having the largest antlers as yet known. " From this survey," says Mr. Dawkins, " it is obvious that the cervine antlers have in- creased in size and complexity from the mid-Miocene to the Pleistocene age, and that their successive changes have been analogous to those that are observed in the antlers of the living deer, which begin with a simple point and increase in number of tines till their limit of growth is reached. In other words, the development of antlers indicated at successive and widely separated pages of the geological record is the same as that observed in the history of a single living species."

Tests for Color-Blindness. Dr. William Thomson, of Jefferson Medical College, has devised a test for color-blindness, for use ! on the Pennsylvania Railroad, which is in a measure self-working, and may be applied with precision by any agent at any station on the line. It is based on Holmgren's system of many-colored yarns, but the number of skeins is reduced from the one hundred and fifty used by Ilolmgren to forty. The forty skeins, each bearing its serial number, are hung by buttons, that can be easily un- hooked, upon a stick about two feet long, in such a way that the numbers are hid. The first half of the series of yarns, num- bered from one to twenty, are devoted to the green test. The odd-numbered skeins are of shades of green, and the even-num- bered ones of "confusion colors" grays, tans, light browns, etc. The other half is similarly occupied with skeins of red, and the " confusion colors " for red-browns, sages, and dark olive, arranged alternately. A man placed before the instrument is told to select ten skeins to match the green test- skein, which is shown him. If his eyes are normal, he will readily select the ten green skeins, and the clerk simply finds the num- bers of the skeins thus selected and puts them down. If the man's eyes are defect- ive, he will hesitate in selecting the skeins ; if color-blind, he will throw out skeins at

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��random of the green and confusion colors. In either case the clerk has only to set down the numbers, which tell the story, and fur- nish the medical man all the facts he needs for making up his judgment. The test is applied in precisely the same way by means of the other half of the stick for red-blind- ness. The reports of the examinations have almost uniformly shown that 4 - 2 per cent of the men are color-biiud.

New Conditions affecting Life in France.

31. A. Legoyt has continued his reviews of the movement of population in France, with a study of the vital statistics of the nation for 18V 9. The population of the country continues to increase, but at a constantly diminishing rate. The hygienic condition of the people has been improved by the prevalence of greater ease in living, the spread of vaccination, and increased scientific exactness in the healing art ; but new causes of mortality, incontestably grave, have been introduced. The chief of these is the excessive use of alcoholic drinks, signalized by the more general con- sumption of liquors distilled from grain and the beet-roct, taking the place of wine, which is likely to increase if the ravages of the phylloxera continue. It is also marked by an increase of arrests for intoxication, of persons found dead, and of suicides, traceable to this cause. The number of suicides has almost quadrupled since 1827, while the population has increased only one- fifth. The growth of mental diseases is also detrimental to public health and lon- gevity. A new cause of mortality worthy of attention is the continued increase in the prices of the necessaries of life, accom- panied by a decrease in the rate of interest on invested funds. The population de- creased in 1879 in twenty-six departments, most of which were in Southern France, where distress was occasioned by the rav- ages of the phylloxera. In details, the vital reports for 1879 show a slight increase of marriages, a few less births, a few more deaths, than were returned in 1878, and a decrease in the excess of births over deaths, which was already small enough. No direct regular relation is discoverable, either in France or in twelve other countries which are compared with it for this view, between

��the proportion, to the thousand, of mar- riages, births, and deaths. Generally, but not always, a greater number of marriages was followed by a greater number of births.

Theories of Comets' Tails. M. Canaille Flammarion suggested an inquiry at a recent session of the French Academy of Sciences, whether the perfect transparency of the tails of comets should not authorize us to believe that they are not material, but an electrical or other excitation of the ether produced by the mysterious star in a di- rection opposite to that of the sun. M. Faye at a subsequent sitting answered this sug- gestion with a material theory, to the effect that the sun appears to be endowed at the same time with two forms of action, one attractive, the other repulsive. The repul- sive force is not proportional to the masses, like attraction, but to the surfaces, and therefore produces effects which are more marked as the matters on which it acts are less dense. It is not exercised through every kind of matter, like attraction, but may be enfeebled or arrested by the interposition of the slightest screen. It is not propagated instantaneously, as attraction is, but succes- sively, like light and heat ; hence its action upon a point in motion is not exercised in the same direction as attraction, although both forces emanate from the same star. Finally, this force varies inversely as the square of the distance, the same as light and heat. The repulsive force operates on the planets and their satellites as well as upon comets, but has escaped attention as to them, in consequence of their compactness. It operates also upon our globe, upon the limits of our atmosphere, but its meteoro- logical effects are masked by the more evi- dent effects of solar radiation which are at work during exactly the same period. Mul- tiple tails to comets are not exceptional, as was till lately believed; that quality has been found to be more general as comets have been observed with more powerful instruments. The recent comet (b, 1881), it is true, seems to have but one tail ; but that is because we are not far removed from the plane of its orbit, within which all the tails are included, so that they appear to us projected upon one another. For the same reason the tail of this comet appears straight.



��If we looked at it from the front instead of in section, its natural curvature would strike every eye. M. Flammarion upheld his elec- trical theory at the succeeding meeting of the Academy, maintaining that no solution of continuity had ever been remarked upon any comet. The tail has always appeared homogeneous, plane, still, like a beam of electric light. He acknowledged that his interpretation was hypothetical, but claimed that his hypothesis was very probable. Might not the electrical illumination, he said, very intense in the nucleus, more fee- ble in the immediate surrounding, be pro- longed into space, impelled by the contrary electrization of the sun ? The phenomena of those long, imponderable, and transpar- ent tails, hitherto unexplained, would then be a simple luminous excitation of the ether.

New Carboniferous Fossils. A consid- erable addition to the fauna of the Lower Carboniferous period has been made by the recent discovery in the shales of Eskdale and Liddesdale on the river Esk, in Scotland, of the fossils of a larger number of new organ- isms than have been obtained from the en- tire Carboniferous system of Scotland for years past. The remains are in an excel lent state of preservation, and in some in- stances are so admirably wrapped up in thin matrices as to retain structures which have never before been recognized in a fos- sil state. Among them are twenty new spe- cies, adding to science five new genera, of ganoid fishes. One of the genera, Tarrasius, is so peculiar that no place can be found for it in any known famliy. Two specimens have been found in such conditions as to leave in doubt some important parts of their structure. Associated with the skele- tons of the fishes are some new phyllopod and decapod crustaceans, one of them hav- ing its intestinal canal distended with food. Several new macrurous decapods occur that differ in no essential respect from their liv- ing representatives. Numerous and often admirably preserved specimens of scorpions have been found, of forms that do not differ essentially, so far as regards external organs, from the living scorpion. Mr. Peach, who describes them, has recognized in them every structure of the recent form, down even to hairs and hooks on the feet. The sting

��alone has not been observed, but the poison- gland has been found. The chief difference lies in the larger proportion of their mesial eyes to the lateral ones, and to the whole ani- mal, than in the living form. These fossils afford no more help in tracing the pedigree of the scorpion than is furnished by the liv- ing form, for they make it obvious that the animal has remained with hardly any change since Carboniferous times. It appears to be the most ancient type of arachnid. Some spe- cies must have included individuals eight or ten inches in length.

Animal Rctribntion. The Boston pa- pers tell a curious story of the retribution which recently came upon a buck, which, by virtue of his superior strength and sa- gacity, had exercised a tyrannous lordship over the herd of deer on the Common, and had thereby excited the hatred of the young- er bucks. The time came when he had to shed his horns. The other bucks gained knowledge of the fact with a marvelous quickness, gathered around him, made a concerted attack upon him and speedily dis- abled him, despite the gallant resistance he tried to make. He was knocked down, butted and kicked till his head and sides streamed with blood, shoved this way and that, with all the fury accompanying each action that the pent-up spite of years could render itself capable of, and, finally, was reluctantly compelled to give up the ghost. Several of the men employed on the Com- mon and public grounds witnessed the af- fray, and attempts were made to drive off the old fellow's assailants, but it was of no use. Each attempt was resented by the infuriated deer, and every man who entered the inclosure with pacific intentions was obliged to flee for his life. The murder having been consummated, the fury of the animals became appeased, and the dead car- cass was removed from the arena.

Permanence of Vegetable Structures.

Dr. Karl Miiller has recently observed a very noteworthy instance of the permanence of vegetable tissues in the case of specimens of mosses that were taken from the ancient viking ship which we described in our May number as having been found last year on the coast of Norway. The mosses had

�� � been buried with the vessel for about a thousand years, yet they retained their structure unimpaired, only they had become browned, or turned to brown-coal, and were easily identified as belonging to Hypnum squarrosum, Climacium dendroides, and other common species. No difficulty was met in making a satisfactory microscopical examination of them, and the cell-structure was brought out as plainly as if they had been freshly gathered. These, however, were only some of the more recent among several ancient specimens of peat-mosses that Dr. Müller reports that he has examined with similar results. The mosses of a tuft supposed to be from the lake-dwellings retained the individuality of their parts; and in a tuft taken from the turf under the drift in the Baltic provinces of Prussia, the plants, older by hundreds of thousands of years than the other specimens, were so well preserved that they were easily recognized by their form and cell-structure as belonging to a Scandinavian species of almost exclusively Arctic growth, which must have come down in the glacial period. We are often surprised at the good condition in which the unfossilized bones of prehistoric men and animals arc sometimes found; but the beautifully preserved condition in which these mosses occur is a far more wonderful phenomenon, because those organisms are among the plants of the slightest structure, and are not subject to fossilization. Still more wonderful is the perfection with which the minute structure of the diatoms is preserved.

Soldering by Pressure.—It is known that Faraday, in 1850, observed that two pieces of ice brought in contact and subjected to pressure would be soldered together, and unite into a homogeneous mass. This soldering, which took place the more readily in proportion as the pieces of ice wore nearer their melting-point, was regarded by Faraday as due to a special property of ice. Mr. W. Spring has recently undertaken a methodical series of experiments in the compression of a variety of bodies. That their condition of division might be well established, he reduced the substances experimented upon to powder, and subjected them in a mold of steel to a pressure of between two thousand and seven thousand atmospheres. Filings of lead were converted at two thousand atmospheres into a solid block, showing no granulation under the microscope, with a density slightly above that of ordinary lead. At five thousand atmospheres the lead became like a liquid, and ran into all the interstices of the apparatus. Powders of zinc and bismuth at five to six thousand atmospheres gave solid blocks, with a crystalline fracture. Approaching six thousand atmospheres, zinc and tin seemed to liquefy. Powder of prismatic sulphur was converted into a solid block of octahedric sulphur. Slack sulphur and octahedric sulphur passed into the same condition. Bed phosphorus passed into the denser state of black phosphorus. Thus, simple bodies undergo chemical transformations under the simple action of pressure. The transformation of amorphous powders, like that of zinc, into crystalline masses, is a kind of auto-combination. Some of the hard metals never lose their pulverulent structure under any pressure. Powders of the bioxide of manganese and the sulphurets of zinc and lead solder under pressure, and present the aspect of natural crystalline pyrolusite, blende, and galena; while silica and the oxides and sulphurets of arsenic do not suffer any agglomeration. Some pulverized salts are solidified by pressure, and become transparent. Hydrated salts—as, for example, sulphate of soda—may be completely liquefied at a high pressure. Certain organic substances—the fatty acids, moist cotton, and starch change their appearance, lose their texture, and undergo a very evident molecular packing.