Scientific Intelligence. — Geology. 227 



others of a manganesian crystalline limestone produced by the 

 same cause, and in which the carbonate of manganese lias com- 

 pletely replaced the magnesia of the magnesian limestone, a 

 kind of isomorphism which Dr J. had not previously seen. 

 Near Boston, a mine of anthracite belonging to the grey wacke 

 formation is traversed by a trap dyke, which has changed the 

 coal at the line of contact into a true graphite. 



10. Height of Waves. — Mr Pentland writes to M. Arago, 

 that in the latitude of Cape Horn, during the most violent tem- 

 pests to which the Stag frigate was exposed, the waves never 

 rose to a greater height than twenty English feet above the 

 mean level of the sea. The greatest height of the waves above 

 the deck of the vessel was eighteen English feet. 



1 1 . Gas of the Sacred Fires of Balwii, near the Caspian Sea. — 

 Several abundant natural sources of combustible gas are known, 

 such as those of the Apennines, and the gas which supplies the 

 gasometer of Fredonia (State of New York), in the neighbour- 

 hood of Lake Erie. But the most remarkable exhalations of 

 gas, both on account of the quantity of gas evolved, and the re- 

 putation which they enjoy among the nations of the East, are, 

 without doubt, those producing what are called the sacred fires 

 of Bakou. No account has hitherto been given of the chemical 

 nature of this gas. M. Hess of Petersburgh having received 

 from M. Lenz a certain quantity carefully preserved in bottles, 

 analyzed it, and ascertained that it is composed of carburetted 

 hydrogen gas, mixed with a little of the vapour of naphtha, and 

 that 100 parts contain — Carbon, 77.5 ; Hydrogen, 22.5 = 100.0. 

 The presence of 24.6 of hydrogen in the 100 parts, would be 

 necessary to make the mixture correspond with the formula 

 C H< ; there is, therefore, a small excess of carbon derived from 

 a minute quantity of carbonic acid. M. Hess ascertained that 

 there is no admixture of olefiant gas, which is so much the more 

 remarkable, because naphtha itself is liquid bicarburetted hydro- 

 gen, and there is every reason to believe that olefiant gas cannot be 

 transformed by heat into carburetted hydrogen. 



12. Volcano of Aconcagua in C/t?ii.— Mr Pentland has ad- 

 dressed a letter to M. Arago, dated the 8th July 18;37, in which 

 he states, that according to several observations he had made, 

 the northern peak of the mountain of Aconcagua, the most elc- 



