De antes secrets TU NUT Xues ma i stil more u are asset i de pe state at dat far I Le art. Te zustier ese fiess, in which petite e 3 e il 10-somet 3 2 ve mow so that at high Zalbenmies tear ama an zmine tren vin rirogen, a fact Which we remianty EL HU L in de sovratory me synthesis of acetylene qe e ammentare i ne deric Mary Stream, Here then we 1274 a de a ne misery. one who is miliar with the themistry of de 17m-amins vil. I zink, e marei to uimit that such wote night have seen formei n me mancity inder the physical conditions exing at the time When he ran ocks were formed.* Given the presence of sich dies in the nondiferentiated mass em which the materials of these mexa were deposited, how cuid mhey be reduced to elementary carbon by the abstraction of their hydrogent In two ways: (a) by direct dasociation of the higher hydro-carbons: marsh-gas and oiefiant gas (e.g.) andergoing this change before our very eyes in the enfiometer under the inft uence of the high temperature of the spark-stream, and depositing carbon on the terminals with much rapidity as to repeatedly bridge over the interspace and close the circuit; (b) by actual reduction under great pressure and high temperature, by the chemical action of strongly positive bases. Perhaps the neareat approach to the physical conditions under which we conceive graphite to have been formed in the fundamental rocks is found in the heated interior of the ordinary fire-clay retorts in use in gas-works. "A very pure and dense

* Do we know absolutely anything as to the origin of the vast stores of hydro-carbons in the oil-fields of America, or of that of the greater stores of the Baku region? Are there any incontestable facts which go to establish an organogenic, in contrariety to a cosmic, origin of those hydro-carbons?

variety of carbon is found in the roof of old gas-retorts, where it has been gradually deposited by the action of the high temperature upon the [hydrocarbons of the] coal-gas which was passing out."* To the influence of high temperature here mentioned I should consider "contact-action" of the heated porous body of the wall of the retort as an important aid towards dissociation and consequent deposition of the carbon.+ All this is quite conceivable as taking place at an early stage of the evolution of the earth.

From these considerations it appears that there is no necessity for regarding the presence of elementary carbon in the form of graphite in the archæan gneisses and schists as indicating pre-existing organic matter.‡

The interpretation of the presence of graphite in the archæan rocks as indicating pre-existing vegetation was admitted even by Prof. Möbius (Der Bau des Eozoon Canadense, § ix) so late as the year 1878. His words are: "Vielleicht rührt der Graphit der Urgneissformation von Organismen her." Kuntze in commenting adversely (Nature, August 28, 1879,) on Möbius' conjecture as to the origin of graphite, denies its phytogenic origin in the Laurentian rocks, though he does not take quite the line of argument which I have in this Note. His objections are of a general nature; and his strongest point is the absence of water in the minerals of the archæan rocks, though perhaps he overstrains this point a little. Of the existence of Kuntze's letter (though I may have read it at the time of its appearance and forgotten it) I was quite unaware while engaged in working out the view which I have ventured to put forward as the probable explanation of the occurrence of graphite: and I only came upon it in looking up afterwards such notices of the Eozoon Canadense controversy as might have appeared since 1878. This was in April, 1888. So convincing to some minds has the presence of graphite appeared as an indication of the pre-existence of vegetation on the Earth, that in the Report of the Smithsonian Institution (1869) quoted by Sterry Hunt (Chemical and Geological Essays, p. 302) the presence of graphite even in aërolites is said to "tell us in unmistakeable language that these bodies came from a region where vegetable life has performed a part not unlike that which [it] still plays on our globe!"

Lockyer's experiments on meteorites (see Nature, vol. xxxiv, p. 280) are of great theoretical interest in this connection. Experimenting on meteorites in a vacuous space with a low-temperature spark-stream he obtained "the same spectrum of hydro-carbons which Huggins, Donati, and others have made us perfectly familiar with in the head of a comet." This seems to support the hypothesis advanced in this Note as to the probable existence of hydro-carbons in the archæan atmosphere of the Earth.

With a high-temperature spark-stream he obtained in a similar manner the hydrogen spectrum, without the carbon spectrum. Is not this due to the temperature of the spark-stream being in this case above that of the dissociation of the hydro-carbon while below that required to give the spectrum of incandescent vapour of carbon? If Mr. Lockyer will repeat this experiment for some time and examine the apparatus afterwards for amorphous carbon-dust, and also examine the spectrum of the spark as it passes between two carbon-points in the synthetic formation of acetylene gas, some interesting results may very likely be obtained tending to give a definite answer to this question.

*

Williamson Chemistry for Students, § 54.

+ See Chemical News, vol. liv, No. 1402, where I have discussed this subject at length.

Since this note was written, it has been announced in Nature, (Dec. 15th, 1887), that "carbon has been found between the lamina" of the great mass of meteoric iron which fell near Cabin Creek, Johnson's County, Arkansas, March 27th, 1886. Graphite "identical in properties with iron-graphite was also identified by Berthelot in the meteoric mass which fell at Cranbourne near Melbourne in 1861.

dissociation of the sulphur components of the coal-gas, along with the deposition of the carbon.

Dissociation by contact-action at a pretty high temperature of portions of the solid crust upon hydro-carbons may be regarded, I think, in the light of such evidence, as a sufficient explanation of the occurrence of graphite in rocks of undoubted archæan age; this therefore need no longer have a phytogenic origin ascribed to it. As a simple corollary to this, it follows that later, say in the stage represented by the Huronian of Prof. R. D. Irving (op. cit.) we should expect to find, under the conditions which he has deduced from his masterly studies of that great group, that, the temperature being too low to induce dissociation, the hydro-carbons would be deposited. Such 'hydrocarbonaceous' material need not therefore be regarded (as he supposes) as 'organic matter' (p. 373) any more than the archæan graphite; and so his argument on this point seems to break down. As for the iron-carbonates of that group, they simply tell us that (on the assumption of their contemporaneous origin) in the Huronian period of the Earth's developement, the temperature in that region was not above the dissociation-temperature of carbonate of iron.

While this was passing through the press, Mr. T. Davies of the British Museum of Natural History was good enough to direct my attention to some very interesting specimens of graphite from Siberia, which are contained in the National Collection, as exhibiting what had appeared to some to be traces of 'organic structure.' From an inspection of them which through Mr. Davies' obliging courtesy I have been able to make, I am convinced that there is no trace whatever of organic structure in them; and that the phenomena which they present can all be explained as the developement of a crude prismatic structure caused by compound cleavage due to compression combined with Answeichungsclivage' accompanied in some cases with a certain amount of crushing along the transverse shearing-planes. See further paper by the author read before Sec. B. (Brit. Assoc., 1888) and published in extenso in the Chemical News, No. 1505.

NOTE M. (cf. p. 59.)

Fossil-evidence of Extension in direction of Cleavage-dip.

The observation that fossils undergo frequent distortion in this direction, and thus afford direct evidence of it in the genesis of a slate, is a very old one. Much has been made lately of the case cited by Heim (see Marr, Brit. Assoc., Manchester, 1887, reported in Nature, loc. cit. Note H.) of Belemnites in the Jurassie slates of Switzerland being parted asunder transversely and the zones interspaced with crystalline calcite. But facts of this nature are not new.

In the Museum of the University of Zürich, as Cotta informs us in a letter from that city dated 1849, there had been collected even then a numerous suite of Belemnites from the Lias-formation, which for the most part had been so altered by squashing (Quetschung) that they could only be recognized as Belemnites by comparison of many examples. These Cephalopods (V.C. goes on to say) “lie in a dark clay-slaty rock, and are for the most part, as it appears, torn assunder (zerissen) into single parts through the squeezing and stretching of the rock in the direction of its cleavage (Schieferrichtung), or they have been stretched out into knotty staves which have now only a faint resemblance to Belemnites. The interspaces (Zwischenräume) in the former cases have been filled with slate." (cf. p. 59 of this work, also Note T. infra).

NOTE N. (cf. p. 78).

Von Cotta is precise in his account of the observations which he made of the serpentinization of granite. He must tell his own tale :

"At Predazzo we happened for the first time to examine one of the places where the limestone and granite are in contact. We selected the rock-wall of the Canzacolli. Not without fatigue we climbed up on the boundary between

the granite and the limestone as far as the great quarry, in which beautiful white marble is obtained, and then still further upwards to where the limestone spreads out over the granite. As far as the marble-quarry we found the boundary everywhere clearly defined and quite sharp. In many instances the granite branched out in vein-like (gangförmig) processes into the limestone, and, (what is especially noteworthy) these at first (at their origin from the massif) undoubtedly granite veins become, as they penetrate further into the limestone, more and more talcose, and very soon pass over into undoubted serpentine-veins, by which the marble moreover is often sharply intersected, as seen in large fragments. The serpentine-veins had been previously observed by Fuchs and Petzholdt; but that they spring [as apophyses] out of the granite, and still consist in part of granite, had no one, so far as I know, before noticed." ("Die Alpen": Weigel, Leipzig, 1881, pp. 196-197).

To leave nothing wanting in the precision of his statement, V. Cotta figures the exact position of the spot where the observation was made, and adds a coloured drawing to shew the exact relation of the serpentine both to the granite and the marble.

NOTE O. (cf. pp. 65-68.)

The Moon's Surface.

Does not Prof. R. S. Ball's theory as to the origin of the Moon suggest an explanation of the result to which Zöllner's investigations have led, that the higher parts of the Moon's surface (those which appear to us illuminated) are composed of materials which on the Earth would be regarded as among the whitest of substances? Can we not follow rationally the Moon in its earlier orbits revolving round the Earth for some time within the limits of the terrestrial atmosphere, then far more extensive than now, if we may judge from the proportionate extent of the present atmosphere of the Sun? And does it not seem highly probable (by all physical considerations) that in the outer perisphere steam and CO2 (and perhaps other acid gases) would be much more abundant than in the lower strata of the Earth's atmosphere, while the surface of the globe itself was still in a glowing liquid state? And would not the comparatively rapid cooling of the smaller lunar mass admit of condensation of carbonated water from the outer terrestrial atmosphere upon the surface of the Moon at an earlier period than that was possible on the surface of the Earth to any very general extent? Have we not here the factors needed for converting the silicates at the surface of the lunar mass into carbonates and free silica to furnish a white rocky outer crust to the Moon? In the absence of a permanent lunar atmosphere and of permanent lunar waters, owing to the greater attractive power of the Earth's mass, and the consequent re-evaporation of any previously condensed free water on the Moon's surface, as that orb passed beyond the limits of the Earth's atmosphere, would not such an early crust remain intact (except where broken through by igneous outbursts) from the absence of disintegrating agents?

Tidal waves. Of course, while the Moon remained unconsolidated earthtides must have been produced in it as the counterpart of the 'lunar tides' produced in the Earth; and these would be so much the greater in proportion to the greater mass of the Earth at any given distance. May not such tides in the Moon in its earlier individual existence along with the more rapid cooling of the smaller lunar mass, explain in part the prodigious size of the mountains as compared with the mass of the Moon itself? May not the 'rills' and 'walled plains' be in such way connected with the earlier 'earth-tides' in the Moon? Again, the appearances presented by such huge lunar volcanoes as Copernicus and some others do not suggest the general radial arrangement of volcanic outflows from a centre (as in terrestrial volcanoes) but a certain rough parallelism in the ridges which bound this and the adjacent craters, as if the craters were but eruptive openings through the crests of great tidal waves in the partly consolidated lunar crust.