CHEMISTRY. 147 



of petroleum. Starting with the nebular hypothesis, the au- 

 thor regards the interior of the earth as metallic, doubtless 

 composed largely of iron and carbides of iron. Through 

 rents made by earthquakes, water gained access to these 

 bodies at a high temperature and under great pressure ; and 

 by their mutual chemical action metallic oxides and satu- 

 rated hydrocarbons resulted. These latter, carried by wa- 

 tery vapor, have spread themselves through the overlying 

 rocks. He gives various geological and chemical facts which 

 go to sustain his hypothesis. 



Coquillion has reinvestigated the conditions under which a 

 mixture of fire-damp and air explodes, originally determined 

 by Davy. He finds the minimum quantity of air which will 

 cause an explosion, when mixed with one volume of marsh 

 gas, to be six volumes, and the maximum quantity sixteen 

 volumes a very wide range. He also observed that while 

 the mixture producing the most violent explosion could be 

 readily ignited by a flame or an electric spark, an ignited 

 palladium wire, carried even to whiteness, caused no explo- 

 sion, but only a rapid diminution of the gases. 



Lawrence Smith has described, in the Annates de Cliimie 

 et de Physique, the gas- wells of Pennsylvania, giving analyses 

 of the gases evolved, made for the State Geological Survey 

 by Professor Sadtler, of the University of Pennsylvania. 

 The marsh gas varies in these products from 60 to 89 per 

 cent., the hydrogen from 4.79 to 22.5 per cent., and the ethyl- 

 ene from 4.39 to 18.12 per cent. Carbonic acid is also pres- 

 ent. 



A committee of the Paris Board of Health has just made a 

 report to the Prefect of Police upon cremation, conceding its 

 feasibility and general advantages, but objecting that it is 

 too readv a means of concealing the evidence of crime. 



Gladstone has examined some candles recovered from the 

 wreck of a vessel sunk off the Spanish coast in 1702, and which 

 have been in sea-water for 173 years. He found that about 

 half the fat had been converted into soaps of calcium and so- 

 dium by the slow replacement of the glycerin. The calcium 

 salt was in excess of the sodium salt. 



Boutmy and Fancher have proposed a new plan for the 

 manufacture of nitroglycerin, by which they have succeeded 

 in making it in large quantities without developing the heat 



