158 COSM )ii. 



do not extend beyond a vertical depth of somewhat more than 

 2000 feet (about one thu'd of a geographical mile) below the 



point) and the relative depth (or that beneath the level of the sea). The 

 greatest relative depth that man has hitherto reached is probably the 

 bore at the new salt-w^orks at Minden, in Prussia: in June, 1844, it 

 was exactly 1993 feet, the absolute depth being 2231 feet. The tern 

 perature of the water at the bottom was 91° F., which, assuming the 

 mean temperature oi" the air at 49°-3, gives an augmentation of tem- 

 perature of 1° for every 54 feet. The absolute depth of the Artesian 

 well of Grenelle, near Paris, is only 1795 feet. According to the ac- 

 count of the missionary Imbert, the fire-springs, " Ho-tsing," of the Chi- 

 nese, which are sunk to obtain [carbureted] hydrogen gas for salt-boil- 

 ing, far exceed o*ir Artesian springs in depth. In the Chinese province 

 of SzU-tschuan these fire-springs are very commonly of the depth of 

 more than 20<,'0 feet ; indeed, at Tseu-lieu-tsing (the place of continual 

 flowj there is a Ho-tsing which, in the year 1812, was found to be 3197 

 feet deep. (HUmboldt, Asie Centrale, t. ii., p. 521 and 525. Annales 

 de r Associati'Mi de la Propagation de la Foi, 1829, No. 16, "p. 369.) 



The relati-7e depth reached at Mount Massi, in Tuscany, south of 

 Vol terra, amounts, according to Matteuci, to only 1253 feet. The bor- 

 ing at the new salt-works near Minden is probably of about the same 

 relative depth as the coal-mine at Apendale, near Newcastle-under- 

 Lyme, in Staffordshire, where men work 725 yards below the surface 

 of the earth. (Thomas Smith, Miner's Guide, 1836, "p. 160.) Unfortu- 

 nately, I do not know the exact height of its mouth above the level 

 of the sea. The relative depth of the Monk-wearfliouth mine, near 

 Newcastle, is only 1496 feet. (Phillips, in the Philas. Mag., vol. v., 

 1834, p. 446.) That of the Liege coal-mine, V Esp6rance, at Seraing, 

 is 1355 feet, according to M. von Dechen, tiie director ; and the old 

 mine of Marihaye, near Val-St.-Lambert, in the valley of the Maes, 

 is, according to M. Gernaert, Ingenieur des Mines, 1233 feet in depth. 

 The works of greatest absolute depth that have ever been formed 

 are for the most part situated in such elevated plains or valleys that 

 they either do not descend so low as the level of the sea, or at most 

 reach very little below it. Thus the Eselschacht, at Kuttenberg, in Bo- 

 hemia, a mine which can not now be worked, had the enormous abso- 

 lute depth of 3778 feet. (Fr. A. Schmidt, Berggesetze der dster Mon., 

 abth. i., bd. i., s. xxxii.) Also, at St. Daniel and at Geish, on the Rorer- 

 btlhel, in the Landgericht (or provincial district) of Kitzbiihl, there 

 were, in the sixteenth century, excavations of 3107 feet. The plans 

 of the works of the Rorerbtihel are still preserved. (See Joseph von 

 Sperges, Tyroler Bergwerksgeschichte, s. 121. Compare, also, Hum- 

 boldt, Gntachten ilber Herantreibung des Meissner Stollens in die Frei' 

 berger Erzrevier, printed in Herder, uber den jetz begonneiien ErbstoU 

 len, 1838, s. cxxiv.) We may presume that the knowledge of the ex- 

 traordinary depth of the Rorerbtihel reached England at an early period, 

 for I find it remarked in Gilbert, de Magnete, that men have penetrated 

 2400 or even 3000 feet into the crust of the Earth. (" Exigua videtur 

 terrte portio, quae unquam hominibus spectanda emerget aut eruitur; 

 cum profundius in ejus viscera, ultra . ^orescentis extremitatis corrupte- 

 1am. aut propter aquas in magnis fodiu. tanquam per venas scaturientes 

 aut propter aeris salubrioris ad vitam o erariorum sustinendam iieces- 

 sarii defectum, aut propter ingentes sum].tus ad tantos labores exant- 

 landos multasqua difficultates, ad profundi- ^res terrae partes peuetrare 



