286 ANNUAL OF SCIENTIFIC DISCOVERT. 



each case is influenced by the pressure to which the heated mass is sub- 

 jected. 



According to the experiments of Bunsen, Hopkins, and others, spermaceti, 

 wax, and paraffine, when heated under powerful pressure, require a higher 

 temperature for their liquefaction than is sufficient to melt them under 

 ordinary circumstances, where the pressing force is only that of a single 

 atmosphere. If, with Hopkins, we assume that the melting point of rocks 

 is in like manner raised by the pressure under which they are placed beneath 

 the surface, we must agree with him in the conclusion that the materials of 

 the earth's crust may retain their solid condition to a much greater depth 

 than has been usually supposed. 



"VVe have, however, no warrant for assuming that all, or even the great 

 mass of rocky materials, obey the same law in regard to their liquefaction 

 as wax and the other similar substances above named. It should be remem- 

 bered that these latter belong to the class of substances which contract as 

 they pass from the liquid to the solid form, while there is another class, 

 typified by ice, in which the act of congelation is accompanied by more or 

 lc?s expansion. Now it has been proved experimentally by Thompson, 

 that pressure, instead of raising, actually lowers the melting point of ice; 

 and there is reason for regarding it as a general law, that all those bodies 

 which expand in becoming solid are similarly affected by pressure, while 

 the other bodies which, like wax, contract in congealing, have their melting 

 point raised under the same circumstances. 



As yet we are too little acquainted with the habitudes of the various 

 rocks in these respects to decide as to the extent to which the one or other 

 of these opposite agencies of pressure upon the melting point may operate 

 in the interior of the globe, or to form any valid conclusion as to their 

 aggregate effect upon the computed thickness of the crust. 



THE COSO MINING REGION OF CALIFORNIA. 



A correspondent of the Aha California Mr. Farley thus describes the 

 geological features of a new mining region in the southeastern part of Cali- 

 fornia, known as the " Coso Mining Region." Its area is about eighty miles 

 square. It has for natural boundaries the Sierra Nevada on the west, the 

 lofty peaks of Owens' Mountains on the north, and an extensive dry lagoon 

 on the east : 



Nature seems to have withheld from the Coso mining district all save 

 mineral wealth that can render a country attractive to man. It is treeless, 

 and, with the exception of boiling springs, waterless, and it is in rare in- 

 stances that even a limited tract of land can be found susceptible of cultiva- 

 tion. Birds are scarcely ever seen, and only deer are found in remote places, 

 where scanty signs of vegetation exhibit themselves. Roaming over the 

 country are a few scattered Indians (the Coso tribe), who, like those of 

 Washoe, live on herbs, roots, and worms. They run swiftly away upon 

 seeing the whites. They build huts of cane, and huddle together in the 

 canons, where they pass a wretched, lazy existence. 



About twenty miles to the southward of Silver Mountain, the party visited 

 an active volcano, at some elevation above the surrounding country, and 

 which threw out hot mud and steam. A curious feature about this was, 

 that, at distances of three feet apart, there were holes, each of which vom- 

 ited forth different colored mud, some scarlet, others a bright yellow, and 



