principle or from what organized body the great mass of our globe has been derived; it is sufficient for us that we exist in a manner where everything is perfectly organized, at least in so far as the aim of our existence is concerned. Many scientific men have exercised their imagination on this problem without being able to come to any definite decision. Some maintain that the nucleus of our globe was a fragment of a body which in its cosmical path had dashed itself into fragments against the sun, which the very close proximity of some comet to that star gives grounds for believing. Others suppose us to be a vast aerolite thrown off from the sun himself * with a force proportional to its mass, to a zone where the motion is determined in accordance with the laws of reciprocal attraction, and that this fragment carried in itself the germ of all that organization which we see around us, and of which we form a part. (Que cet éclat portait en lui le germe de toute cette organisation que nous observons ici et dont nous faisons partie.) They suppose the satellites to be small parts or fragments detached from the chief mass by the violence of the rotation at the time it is hurled forth, or by the excessively high original temperature, increased by the fall, which produced a very violent dilatation of the matter, and severed some portions from it. These aerolites, it is said, by way of comparison, contain within them the principle common to the body whence they have been derived, just as a grain of seed carried by the wind is able to produce at a remote distance a tree like its prototype, with such modifications only as are due to soil or climate."

In the spring of 1871 Professor Helmholtz delivered at Heidelberg and at Cologne a discourse on the origin of the solar system, which he printed in the third collection of his interesting "Populäre wissenschaftliche Vorträge," pablished last year. He directed attention on that occasion to the facts that meteorites sometimes contain compounds of carbon and hydrogen, and that the light emitted by the head of a comet gives a

* He alludes here in a note to the theory held by Laplace and others.

"Populäre wissenschaftliche Vorträge. Von H. Helmholtz." Braunschweig: Vieweg und Sohn. 1876. Drittes Heft. p. 135.

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spectrum which bears the closest resemblance to that of the electric light when the arc is surrounded by a gaseous hydrocarbon. Carbon is the characteristic element of the organic compounds of which all things living are built up. Who can say," he asks," whether these bodies which wander about through space may not also strew germs of life where a new heavenly body has become fitted to offer a habitat to organized creatures?" The hypothesis, in the form set forth in 1871 by Professor Helmholtz and Sir William Thomson, was vigorously handled by Zöllner, of Leipzig, whose work, "Ueber die Natur der Cometen," appeared in the following year. In the Vorrede of his book he passes his countryman by unmentioned, but declares Sir William Thomson's proposition to be unscientific, and that in a twofold sense. In the first place, he maintains it is unscientific in a formal or logical sense, in that it changes the original simple question, Why has our earth become covered with organisms? into a second, Why had that heavenly body the fragment of which fell upon our planet become covered with vegetation, and not our earth itself? "If, however," he adds, "bearing in mind an earlier dictum,* we regard inorganic and organic matter as two substances from all eternity diverse, just as in accordance with our present views we consider two chemical elements to be diverse, such an hypothesis as that now advanced must be at variance with the destructibility of organisms by heat which experience has taught us."

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Again," contends Zöllner, "the hypothesis in its material bearing is unscientific. When a meteorite plunges with planetary velocity into our atmosphere, the loss of vis viva arising from friction is converted into heat, which raises the temperature of the stone to a point where incandescence and combustion take place. This, at all events, is the theory at present generally held to explain the phenomena of star-showers and fire-balls. A meteorite, then, laden with organisms, even if it could withstand the sundering of the parent mass unscathed, and should take no part in the general

"Dead matter cannot become living matter unless it be subject to the influence of matter already living.'

rise of temperature resulting from this disruption, must of necessity traverse the earth's atmosphere before it could deliver at the earth's surface organisms to stock our planet with living forms."

Helmholtz did not long delay in replying to Zöllner's criticism on this question. An opportunity occurred during the publication, in the following year, 1873, of the second part of the German translation of Thomson and Tait's Handbook of Theoretical Physics." The preface contains Helmholtz's answer. He points to the fact, confirmed by numerous observers, that the larger meteoric stones, during their transit through our atmosphere, become heated only on the outer surface, the interior remaining cold-often very cold. Germs which may happen to lie in the crevices of such stones would be protected from scorching while travelling through the air. Those, moreover, which lie on or near the surface of the aerolite would, as soon as it entered the upper and most attenuated strata of our atmosphere, be blown off by the swift and violent current of air long ere the stone can rend those denser layers of our gaseous envelope where compression is sufficiently great to cause a perceptible rise of temperature. As regards that other point of debate, referred to by Thomson only, the collision of two cosmical masses, Helmholtz shows that the first result of contact would be violent mechanical movement, and that it is only when they begin to be worn down and destroyed by friction that heat would be developed. It is not known whether this may not continue for hours or days, or even weeks. Such portions as at the first moment of contact are hurled away with planetary velocity may consequently be driven from the scene of action before any rise of temperature may have taken place. "It is not impossible," he adds, that a meteorite or a swarm of meteorites, in traversing the upper layers of the atmosphere of a heavenly body, may either scatter from them or carry with them a quantity of air containing unscorched germs. These are possibilities which are not yet to be taken as probabilities; they are questions which, from the fact of their existence and range, are to be kept in sight, so that, should a case arise, they may receive an answer either

by actual observations or by some conclusive deduction." It should be mentioned here that these views of Helmholtz's are also to be met with in a supplement to his lecture on the origin of the solar system.

He

In tracing the gradual development of this important controversy we now arrive at the present year, and proceed to discuss the allusion made to it by Professor Allen Thomson in his address at Plymouth. The difficulty regarding the origin of life is, he considers, not abolished, but only removed to a more remote period, by the supposition of the transport of germs from another planet, or their introduction by means of meteorites or meteoric dust; for, besides the objection arising from the circumstance that these bodies must have been subjected to a very high temperature, we should still have everything to learn as to the way in which the germs arose in the far distant regions of space from which they have been conveyed. At one of the Sectional meetings, a few days later, Sir William Thomson made these observations the text of a further communication on the now well-worn subject. desired to limit the discussion to the bare dry question, Was life possible on a meteorite? The hypothesis which was to explain the bringing of life to our earth did not pretend to explain the origin of life, and he would not attempt to offer an explanation of the origin of life. The three questions which presented themselves were these: Was life possible on a meteorite moving in space? Was life possible on a meteorite while falling to the earth's surface? and, Could any germs live after the meteorite had become imbedded in the earth? A meteorite may be exposed to great heat before it reaches the earth; whether or not life on that meteorite would be destroyed by that heat was dependent on the duration of exposure. If a meteorite traversed space with the same side always exposed to the sun that side would be strongly heated, the other would be cold; if it spun round at a uniform rate all its surface would be of one uniform temperature; and if it rotated once per hour it would have a high temperature on one side and be as cold as ice on the other. The whole or part of the surface of a meteorite might afford a climate

suitable to some living forms, destructive to others. When the moss-covered stone enters the atmosphere the germs upon its surface would be torn off long before the stone became heated, and in a few years they may settle down on the earth, take root, and grow. But were the germs of the exterior destroyed by heat, there might still be vegetable life in the interior. The time occupied by a stone in its passage through the air would not be more than twenty or thirty seconds at the outside, so that the crust might be fused, while the interior might have a moderate temperature, and anything alive in it would fall to the earth alive. Sir William Thomson concluded by remarking that after the collision of cosmical masses fragments must be shot off, some of which must certainly carry away living things not destroyed by the shock of the collision, and he did not hesitate to maintain, as a not improbable supposition, that at some time or other we should have growing on this earth a plant of meteoric origin.

Nothing bearing the semblance of a plant or even of its seed has as yet been met with in a meteorite; nor have any of the masses which have fallen on our planet shown anything approaching the structure which distinguishes sedimentary rocks from those of a purely plutonic character. The occurrence, however, in them, or with them, of organic compounds, of compounds of carbon and hydrogen, which it is hard to suppose could owe their existence to any other agency than that of life itself, and which represent the final stage previous to their final destruction, has now been so frequently noticed that I have put together in chronological order what information in this direction from a "world ayont" the meteorites have brought to us.

1806. March 15th, 5 P.M.-Two stones, weighing together six kilogr., fell at Alais, Dép. du Gard, France. They have the appearance of an earthy variety of coal; the color of the crust is a dull brownishblack, so is that of the interior. The structure is very soft and friable. When heated it emits a faint bituminous odor. It was examined at the time of its fall by Thénard and a Commission appointed by the Institute of France. The French observers found it to contain 2.5 per cent. of carbon; while Berzelius, in 1834

estimated the amount of carbon present to be 3.05 per cent. In 1862 Roscoe submitted this meteorite to a very thorough investigation. He found the carbon present to amount to 3.36 per cent. Ether dissolved 1.94 per cent. of the stone; the solution on evaporation left crystals which have an aromatic odor, and a fusing-point of 114° C., and which sublime on the application of heat, leaving a slight carbonaceous residue. The crystals really appear to be of two kinds : acicular crystals, which are sparingly soluble in absolute alcohol, but are readily taken up by ether, carbon disulphide, turpentine, and cold nitric acid, and dissolve in cold sulphuric acid, striking a brown color; and rhombic crystals, which dissolve in ether and carbon disulphide, but are unaffected by cold nitric acid, sulphuric acid, or turpentine. An analysis of 0.0078 gramme of the crystals soluble in alcohol gave the following numbers :

The atomic ratio of carbon to hydrogen, then, is nearly 1: 1, or that of the reddish-brown and colorless mineral resin könleinite, which occurs in crystalline plates and grains in the lignite of Uznach, in Switzerland. Kraus makes the fusingpoint of könleinite 114° C.; it is slightly soluble in alcohol, but much more soluble in ether. Dr. Lawrence Smith, who has recently examined the Alais meteorite, arrives at the same results as Roscoe; and also that the carbonaceous ingredient of this meteorite resembles in all its physical characters those of a substance which he obtained from the graphite of the Sevier-County meteoric iron, to which I shall presently refer.

1838. October 13th, 9 A.M.-At the hour mentioned a great number of large stones fell over a considerable area at Kold-Bokkeveld, seventy miles from Cape Town. Those which fell near Tulbagh are estimated to have weighed many, hundredweights. It is said that they were soft when they fell, but became hard after a time. This material has a dull black color, and is very porous and friable. Harris, who analysed it in

1859, determined the presence of 1.67 per cent of carbon, and somewhat more than 0.25 per cent. of an organic substance soluble in alcohol. This compound is described as possessing a yellow color, and a soft resinous, or waxy, aspect. It readily fused with a slight rise of temperature, and when heated in a tube it was decomposed, emitting a strong bituminous odor, and leaving a carbonaceous residue. Some four years ago I was considering what should be done with a trace of this substance, so small in amount that it could not be removed from the vessel containing it. I was unwilling to throw away even so small a quantity of so precious a substance, so I drew off the neck of the flask and placed it in a dark cupboard of a room, the temperature of which, during the greater part of the year, is unusually high. In the interval this organic compound has sublimed, and is deposited on the higher parts of the vessel in colorless and well-defined crystalline plates.

1840. During this year a large mass of meteoric iron was discovered in Sevier County, Tennessee, enclosing a large nodule of graphite. "It is," writes Dr. Lawrence Smith, "the largest mass of graphite which has come under my observation, and is perhaps the largest known." Its dimensions are 60mm by 20mm and 35mm, and it weighs 92 grammes. Two grammes of this nodule were reduced to powder and treated with ether, and the liquid on evaporation left a residue weighing 15 milligrammes, and possessing an aromatic, somewhat alliaceous, odor. It consisted of long colorless acicular crystals, others which were shorter. as well as some rhomboidal crystals and rounded particles. This extracted substance melted at about 120° C. When heated in a tube closed at one end it melts and then volatilizes, condensing in yellow drops, and leaving a carbonaceous residue. Dr. Lawrence Smith believes that the three elements, carbon, hydrogen, and sulphur, which they contain, may be in combination, and he has named the meteoric sulphohydrocarbon "celestialite."

1857. April 15th, 10.11 P.M.-A brilliant detonating meteor was observed at this hour over Kaba, S.W. of Debreczin, Hungary, and a meteorite weighing 4 kilogr. was found on the following morn

ing imbedded in the hard surface of a road close by. The crust is black, and the mass of the stone dark grey; throughout the structure black portions of the size of peas lie scattered, giving the stone a porphyritic character. Wöhler treated the stone with alcohcl, which removed a white, apparently crystalline, substance possessing a peculiar aromatic odor. With ether it broke up into oily drops, and appeared to be decomposed into an insoluble fluid body and a soluble solid portion. The solid substance was obtained in a distinctly crystalline condition on driving off the ether. It volatilizes in air, fuses in a closed tube, and is decomposed when greater heat is applied, a fatty odor being observed, and a black residue left. The hydrocarbon is believed by Wöhler to be allied to ozocerite or scheererite. When the pow

dered stone is heated in oxygen it turns of a cinnamon-brown color. This meteorite contains 0.58 per cent. of carbon.

1861.-The huge mass of meteoric iron discovered at Cranboune, near Melbourne, Australia, in 1861, encloses more or less rounded masses of carbon. They are pronounced by Berthelot, who has submitted some of the material to the most powerful oxidizing reagents, to resemble the form of carbon which separates from cast-iron on cooling rather than native graphite.

1864. May 14th, 8 P.M.-On this occasion more than twenty stones fell at Montauban, Tarn et Garonne, France, some of them being as large as a human head, and most of them smaller than a fist. The appearance which this meteorite exhibits closely resembles that of a dull-colored earthy lignite. The masses are black and very friable, and fall to powder when placed in water; this is due to the removal of the soluble salts which cement the ingredients together. A shower of rain would have destroyed them One hundred parts of this stone contain 5.92 parts of carbon itself, partly as a constituent of one organic compound, which Cloëz found to possess the following composition :

the body of which this is a decomposed product by means of hydriodic acid, and obtained a considerable quantity of the hydrocarbon C2H2n+2 analogous to rockoil. The reduction takes place less readily in this case than in that of coal. Dr. Lawrence Smith finds the combustible portion of the material to amount to about 4.5 per cent.

1867. This Indian meteorite, which fell at Goalpara about the year 1867 (the exact date is not known), was examined by Tschermak, who found it to contain 0.85 per cent. of a hydrocarbon. The quantity, though small, materially affects the general appearance of the stone; it can be recognized under the microscope as a smoky-brown, lustreless ingredient accompanying the fragments of nickeliron. Of the 0.85 per cent. 0.72 is carbon and 0.13 hydrogen. Tschermak suggests that the luminous phenomena so often attending the fall of an aerolite and the "tail" left by many meteors and shooting stars may be due to the combustion of compounds of which carbon forms an important constituent.

1868. July 11th.-The curious meteorite of dull grey hue and loose structure which fell on this day at Ornans, Doubs, France, partly owes its dark color to the presence of a hydrocarbon.

1869. January 1st, 12.20 P.M.-A most remarkable fall of stones took place on New Year's Day, 1869, at Hessle, near Upsala; it is the first aerolitic shower recorded to have taken place in Sweden. The meteorites have so loose a structure that they break in pieces when thrown with the hand against the floor or frozen ground. The most interesting feature of the Hessle fall is the association with the stones referred to of matter mainly composed of carbon. The peasants of Hessle noticed that some of the meteorites which fell on the snow near Arnö soon crumbled to a blackish-brown powder resembling coffee-grounds. Similar powder was found on the ice at Hafslaviken in masses as large as the hand, which floated on water like foam, and could not be held between the fingers. A small amount secured for examination was found under the microscope to be composed of small spherules; it contained particles extractible by the magnet, and when ignited left a reddishbrown ash.

Heated in a closed tube it

The combustible ingredient appears to have the composition n C,H,O,. It was noticed on this occasion that the stones found in the same district with the carbonaceous substance, were, as a rule, quite round and covered on all sides with a black, dull, and often almost sponge-like, crust. The iron particles on the surface of the smaller stones were usually quite bright and unoxidized, as though the stone had been heated in a reducing atmosphere. Nordenskjöld, who examined them, expresses the belief that this carbon compound frequently, perhaps invariably, occurs in association with the meteorites, and he attributes its preservation in this case to the fall of the stones on snow-covered ground.

1870. During this year the Swedish Arctic Expedition discovered in the basalt of Ovifak, near Godhavn, Island of Disko, Greenland, some enormous metallic masses which are generally regarded as blocks of meteoric iron. Like meteoric iron, they contain nickel and cobalt, but, unlike that iron, they are but slightly attacked by hydrochloric acid. The metal, moreover, when heated evolves more than 100 times its volume of a gas which burns with a pale blue flame, and is carbonic oxide mixed with a little carbonic acid; after this treatment the substance dissolves in acid, leaving a carbonaceous residue. The composition of this remarkable "iron," if we may call it by that name, has been found by Wöhler to be as follows: