TERRESTRIAL PHENOiMENA. 159 



leve, of Ihe sea, and consequently only about e^Vo^^ ^^ the 

 Earth's radius. The crystalhne masses that have been erupt- 

 ed from active volcanoes, and are generally similar to the 

 rocks on the upper surface, have come from depths which, 

 although not accurately determined, must certainly be sixty 

 times greater than those to which human labor has been ena- 

 bled to penetrate. We are able to give in numbers the depth 

 of the shaft where the strata of coal, after penetrating a cer- 

 tain way, rise again at a distance that admits of being accu- 

 rately defined by measurements. These dips show that the 

 carboniferous strata, together with the fossil organic remains 

 which they contain, must lie, as, for instance, in Belgium, 

 more than five or six thousand feet* below the present level 



uon possumus; adeo ut qiiadringentas aut [quod rarissime] quhigentas 

 orgyas in quibusdam metallis descendisse, stupendus omnibus videatur 

 conatus." — Gulielmi Gilberti, Colcestrensis, de Magnete Physiologic 

 ncva. Lond., 1600, p. 40.) 



The absolute depth of the mines in the Saxon Erzgebirge, near Frei 

 burg, are: in the Thurmhofer mines, 1944 feet; in the Honenbirke • 

 mines, 1827 feet ; the relative depths are only G77 and 277 feet, if, iu 

 order to calculate the elevation of the mine's mouth above the level of 

 the sea, we regard the elevation of Freiburg as determined by Reich's 

 recent observations to be 1269 feet. The absolute depth of tlie cele- 

 brated mine of Joachimsthal, in Bohemia (Verkreuzunsj des Juns: Hauer 

 Zechen-and Andreasganges). is full 2120 feet ; so that, as Von Dechen's 

 measurements show that its surface is about 2388 feet above the level 

 of the sea, it follows that the excavations have not as yet reached that 

 point. In the Harz, the Samson mine at Andreasberg has an absolute 

 depth of 2197 feet. In what was formerly Spanish America, I know 

 of no mine deeper than the Valenciana, near Guanaxuato (Mexico), 

 where I found the absolute depth of the Flanes de San Bernardo to be 

 1686 feet ; but these planes are 5960 feet above the level of the sea. 

 If we compare the depth of the old Kuttenberger mine (a depth great- 

 er than the height of our Brockeu, and only 200 feet less than that of 

 Vesuvius) with the loftiest structures that the hands of man have erect- 

 ed (with the Pyramid of Cheops and with the Cathedral of Strasburg). 

 we find that they stand in the ratio of eight to one. In this note I have 

 collected all the certain information I could find regarding the great- 

 est absolute and relative depths of mines and borings. In descending 

 eastward from Jerusalem toward the Dead Sea, a view presents itself 

 to the eye, which, according to our present hypsometrical knowledge 

 of the suriace of our planet, is unrivaled in any country; as w^e ap- 

 proach the open ravine through which the Jordan takes its course, we 

 tread, with the open sky above us, on rocks which, according to the ba- 

 rometric measurements of Berton and Russegger, are 1385 feet below the 

 level of the Mediterranean. (Humboldt, Agie Centrale, lb. ii., p. 323.) 



* Basin-shaped curved strata, which dip and reappear aV measurable 

 distances, although their deepest portions are beyond the reach of the 

 miner, afford sensible evidence of the nature of the earth's crust at great 

 depths below its surface. Testimony of this kind possesses, consequent- 

 ly, a ^eat s:ei;2nostic interest. I am indebted to that excellent ":eog. 



