228 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



served by Duhrnberg, medical inspector, as a product of de- 

 composition, incrusting the almost vertical dark-gray schis- 

 tose rock on the banks of the Irtish, which was called mount- 

 ain-butter by the natives, and also used by them as a sedative 

 for wounds and an astringent. The adhering rock, inclosing 

 microscopic crystals of pyrites, indicated its origin and mode 

 of formation very clearly; and chemical analysis by Schmidt 

 showed that, although similar in other respects to the Yenisei 

 salt, it contained a much larger amount of sulphate of lime 

 in place of sulphate of ammonia, which was entirely wanting. 

 Both seem to result from the oxidation of the sulphurets ac- 

 companying the feldspathic and angite rocks, and the de- 

 composition of these rocks by the nascent sulphuric acid 

 formed. 18 G,May 13, 1874, 300. 



COMPOSITION OF FULGURITES. 



Fulgurites or sand-tubes, usually regarded as formed of 

 silica, fused by electrical discharges, according to analyses 

 by Scholz, consist essentially of carbonates of the alkaline 

 earths, about 85 per cent, being carbonate of lime, and 11 per 

 cent, carbonate of strontia. 14 (7,00X1., 408. 



ATMOSPHERIC DUST. 



M. Tissandier has lately been prosecuting extended inqui- 

 ries into the character and amount of atmospheric dust pre- 

 cipitated upon given surfaces, and finds occasion to conclude 

 that this amount is quite enough to play an important part 

 in the physics of our globe. This dust he found to contain 

 one third of combustible organic matter and two thirds of 

 mineral matter. Iron is almost always present, and this, in 

 M. Tissandier's opinion, has an important bearing upon the 

 question of iron meteorites. He thinks also that a consider- 

 able part of this atmospheric dust is received from the plan- 

 etary space. 3 B, April 2, 1874, 623. 



GEOLOGICAL COLLECTION AT THE CENTENNIAL EXPOSITION. 



With a view of properly exhibiting the geological and 

 metallurgical resources of America at the forthcoming expo- 

 sition at Philadelphia, an association has been organized, em- 

 bracing such names as those of Professor Lesley, Professor 

 Genth, Professor Raymond, Professor T. Sterry Hunt, Pro- 



