172 QUICKSILVER DEPOSITS OP THE PACIFIC SLOPE. 



The foregoing pai-agi-aph contains no novel statement. Scrope,^ in 

 1825; MacCullocli," in 1831; and filie de Beaumont,^ in 1847, all maintained 

 that the primeval rock from which the strata are derived must have been 

 granitic. In 1859 Mr. Daubree* entei'ed more fully into the physical theory 

 of the formation of the primitive rocks. Taking as a basis Humboldt's 

 estimate of the mean depth of the ocean (3,500 meters), he calculated that 

 the barometric pressure of the sea water alone in the form of vapor would 

 amount to almost exactly two hundred and fifty atmospheres, or say 3,700 

 pounds per square inch. Later estimates of the area and deptli of the sea 

 diminish this figure somewhat, but only to tlie extent of about a hundred 

 pounds.' When the temperature of the earth was too high to permit of the 

 condensation of water, this pressure was further augmented by other vapors 

 and gases. The purely igneous rocks formed prior to the condensation of 

 any water, as Daubrue infers, must have been changed by the action of the 

 water first precipitated at very high temperatures and pressures into a mass 

 of crystallized minerals, exactly as in his own experiments in sealed tubes 

 crystals were developed from amorphous materials. Inquiring whetlier the 

 earliest aqueous precipitation corresponds to the period of the formation of 

 granite, he replies that we cannot affirm this in an absolute manner, but 

 may presume it. This presumption of Mr. Daubree, previously indicated 

 by others on less satisfactory grounds, seems to me to gain greatly in force 

 by the reasons which I have adduced above. My argument shows it 

 utterly improbable that the rocks which antedate the formation of consid- 

 erable seas should even now be everywhere concealed, while it is well 

 known that the lowest visible rocks the world over are granitic. In 1879, 

 again, Mr. R. Mallet" speculated upon tlie character of the earliest seas. He 



' Considerations ou A'^olcanoes Leading to the Establishment of a NewTIieory of the Earth, quoted 

 by Dr. Hunt, Origin of Crystalline Rocks, sec. 17. 



- System of Geology, vol. 2, p. 83. "That very granite," he adds, "may be visible; bnt we can- 

 not as yet distinguish it from the many snccessive ones which have acted in the elevation of the 

 strata." 



' Bull. Soc. g^ologiqnc France, 2d series, vol. 4, pp. 1321 et seq. He regards granite as formed by 

 igneo-aqueons fusion and speaks (p. 1327) of " the first granitic crust of the terrestrial globe." 



^Etudes et esper. syntb. sur le metam : Ann. des mines, .5th series, vol. 16, p. 471. 



''Dr. Kriimmel's revision of the question of the total quantity of water in the ocean (extract from 

 a note to the Gottiugon Academy, Nature, vol. 19, 1S79, p. 348) leads to about 3,584 pounds per square 

 inch. 



•■' Quart. Jour. Geol. Soc. London, vol. 36, 1880, p. 112. 



