E. MINERALOGY AND GEOLOGY. 221 



dogne. The vein is of quartz, traversing a very coarse por- 

 phyric granite, and contains, in addition to bismuth, the 

 minerals of tungsten, iron pyrites, and some ores of lead. 

 The bismuth occurs native in the sulphide, and as subcar- 

 bonate, the latter ore predominating. In this respect the 

 mine seems to differ from all other mines hitherto worked, 

 the difference having led to the adoption of a new method 

 for extracting the metal. The finely crushed mineral is sev- 

 eral times treated with hydrochloric acid, and the valuable 

 portions of the mixed ores thus dissolved. Into the filtered 

 solution, which should be but slightly acid, bars of iron are 

 introduced, by which means the bismuth is entirely precipi- 

 tated as a heavy, black powder. This powder is quickly 

 washed with pure water, and, before it has time to oxidize in 

 the air, is compressed in a mould and dried rapidly in an 

 oven. The dried mass is then fused in a closed black-lead 

 crucible under a thick layer of charcoal for about three 

 quarters of an hour, and is afterward cast into ingots. The 

 metal, thus obtained, contains traces of lead, of arsenic, and 

 of antimony, and can be purified in the ordinary way. The 

 new method of extraction has thus far served very well, the 

 loss of metal being much less than by the older processes. 

 Loss by volatilization is especially avoided. Up to this time 

 the new mine has furnished about two hundred and fifty 

 kilogrammes of bismuth to commerce, this product being 

 mainly consumed in Central France for pharmaceutical pur- 

 poses. 1 B, February 22, 1874, 352. 



mallet's observations on the properties of rocks. 



The general seismic views of Mallet have already been 

 partially presented to the world in various publications, but 

 it is only lately that the complete memoir presented by him 

 to the Royal Society has reached America. Passing by those 

 views which may be considered more or less theoretical, al- 

 though apparently very firmly established, we come to the 

 experimental determinations that have occupied so much of 

 Mr. Mallet's time, and that must ever remain an invaluable 

 contribution to our knowledge of terrestrial physics. The 

 two great questions, he states, that are to be answered, are 

 how much heat is produced by the crushing of a given 

 weight or volume of rock, and whether the total amount of 



