178 Reviews — Chemical Geology. 



Mr. Ansdell have found hj'drogen in both gneiss and felspar. 

 Professor Tilden has now examined granophyre from Skye, gabbro 

 from the Lizard, pyroxene gneiss from Ceylon, gneiss from Seringa- 

 patam, and basalt from Antrim, and he finds all to yield permanent 

 gas when the rocks are heated in a vacuum. This gas varies in 

 amount from a volume about equal to that of the rock to about 

 eighteen times that volume. It usually consists of hydrogen in 

 much larger proportion than that found by the observers just 

 quoted, together with carbon dioxide and smaller quantities of 

 carbon monoxide and hydrocarbons. 



Eeferring to the presence of marsh gas (C H^) in the several rocks 

 examined, Professor Tilden observes that the occurrence of this 

 gas, and the production of large quantities of hydrocarbonous gases, 

 as well as liquid petroleum, in many parts of the earth's surface, 

 tend to support the view, v^^hich is apparently gaining ground, that 

 in the interior of the earth's crust there are large masses, not only 

 of metal, but of compounds of metals, such as iron and manganese, 

 with carbon. Assuming the existence of such material, it is easy 

 to conceive how, by the action of water at an elevated temperature, 

 it may give rise to metallic oxides and mixtures of hydrogen with 

 paraffinoid and other hydrocarbons. This view was put forward 

 some years ago by Mendelejeflf, and has been supported in tlie 

 article, previously noted, by Moissan. 



III. — Chemical Geology : Etude des Cakbures Metalliques. 

 By M. Henri Moissan. Proc. Royal Soc, vol. Ix (1896), p. 156. 



rnHE author gives a summary of his remarkable researches on 

 i the formation of metallic carbides by the aid of the electric 

 furnace, and on the compounds produced by the action of water 

 on these bodies. 



The carbides of calcium, strontium, barium, and lithium, when 

 acted upon by water at ordinary temperatures, give rise to pure 

 acetylene. Carbide of aluminium gives rise to pure marsh gas. 

 Carbides of cerium, lanthanum, yttrium, and thorium yield a mixture 

 of acetylene and mai'sh gas. Carbide of manganese ^'ields a mixture 

 of marsh gas and hydi'ogen. Carbide of uranium gives rise to 

 marsh gas, hydrogen, ethylene, and also to solid and liquid hydro- 

 carbons. 



The author calls attention to the bearing of the facts on certain 

 geological problems. Exhalations of marsh gas may, in certain cases, 

 be due to the action of vi^ater on carbide of aluminium. Petroleum and 

 allied compounds, which are in some instances undoubtedly due to 

 the decomposition of organic matter, may in others be formed by 

 the action of water on certain metallic carbides at a high temperature, 

 as suggested by Mendelejeff. 



It is probable that in the early periods of the eartli's history 

 nearly the whole of the carbon was combined with the metals. 

 The intervention of water w^ould give rise to hydrocarbons, and 

 these by oxidation would produce carbonic acid. The assumption 



