NOTES TO PRECEDING SECTION. 



117 



composed of distinct nebulse as the other of stars"), and far- 

 ther in his letter to me of March 1829. 



84 (p. 48.)— Sir John Herschel, Astron. ^ 585. 



86 (p. 48.)-Arago, in Annuaire, 1842, p. 282—285, 409— 

 411, and 439—442. 



86 (p. 48.)— Olbers on the Transparency of Universal 

 Space, in Bode's Jahrbuch, 1826, s. 110—121. 



87 (p. 48.)—" An opening in the heavens." Sir William 

 Herschel, in the Transact, for 1785, vol. Ixiv. Pt. i. p. 256 ; 

 Le Francais Lalande, in the Connaissance des terns pour 

 Tan viii. p. 383 ; Arago, in Annuaire, 1842, p. 425. 



88 (p. 48.)— Aristot. Meteor, ii. 5, 1 ; Seneca, Natur. 

 QuBESt. i. 14, 2 ; " coelum discessisse," in Cic. de Divin. i. 43. 



89 (p. 48.)— Arago, in Annuaire, 1842, p. 429. 



90 (p. 48 ) — In December 1837 Sir John Herschel saw the 

 star rj Argo, which had hitherto appeared of the second mag- 

 nitude, and quite unchanging, increase rapidly to the first 

 magnitude. In January 1838 the intensity of its light was 

 still equal to that of a Centauri. According to the latest in- 

 telligence, Maclear, in March 1843, found the star as brill- 

 iant as Canopus : a Cruris appeared quite misty beside rj 

 Argo. 



91 (p. 48.) — '* Hence it follows that the rays of light of the 

 remotest nebulae must have been almost two millions of 

 years on their way, and that, consequently, so many years 

 »go this object must have had an existence in the sidereal 

 heaven, in order to send out those rays by which we now 

 perceive it." William Herschel, in the Transact, for 1802, 

 p. 498; John Herschel, Astr. t) 590; Arago, in Annuaire, 

 1842, p. 334, 359, and 382-385. 



92 (p. 49.) — From a beautiful sonnet of my brother, Frei- 

 heit und Gesetz (Wilhelm von Humboldt, Gesammelte 

 Weike, Bd. iv. S. 358, No. 25). 



93 (p. 49.)— Otfried Muller, Prolegomena, S. 373. 



94 (p. 50.) — It is proper to distinguish between the abso- 

 lute depth to which man has penetrated in his mining opera- 

 tions, or the depth from the surface of the earth at the place 

 ■where the operations are carried on, and the relative depth, 

 i. e. the depth below the level of the sea. The greatest rel- 

 ative depth that has been reached is, perhaps, the bore at 

 New-Salzwerk, Minden, in Prussia. In June 1841 it was 

 exactly 1844i Parisian feet ; the absolute depth, was, how- 

 ever, 2094^ Par. feet. The temperature of the water in the 

 deepest bore was 32 7° C. (90 8° F.) which, assuming 9 60 C. 

 as the mean temperature of the air, gives a rise of lOO for 

 296 metres (upwards of 97*6 feet English). The Artesian 

 well of Crenelle, at Paris, is only 1683 feet in absolute 

 depth. From the accounts of the missionary Imbert from 

 China, the depth of our Artesian wells is far surpassed by 

 that of the fire-spring Ho-tsing, which yields inflammable 

 gas employed in salt boiling. In the Chinese province Szii- 

 tschuan, these fire-springs are said very commonly to reach 

 a depth of from 1800 to 2000 feet; and at Tseu-lieu-tsing 

 (place of perpetual flax), a Ho-tsing, bored with the rod in 

 the year 1812, is reported to extend to the depth of 3000 

 feet (Humboldt, Asie centrale, t. ii. p. 521 and 525 ; An- 

 nales de I'Association de la Propagation de la Foi, 1829, No. 

 16, p. 369). The relative depth attained at Monte Massi, 

 in Tuscany, south from Volterra, according to Matteucci, is 

 but 1 175 feet. The bore at New-Salzwerk approaches very 

 nearly in relative depth the coal pit at Apendale, New-cas- 

 tle-under-Lyme (Staflfordshire). There the works are car- 

 ried on 725 yards, or 2045 French feet, under the surface 

 (Th. Smith, The Miner's Guide, 1836, p. 160). Unfortu- 

 nately, the height of the ground above the level of the sea 

 is not accurately ascertained. The relative depth of the 

 Monkwearmouth pit, near Newcastle-on-Tyne, is only 1404 

 feet (PhiUijTS, Philos. Mag. vol. v. 1834, p. 446) ; that of 

 the Esperance pit, at Liege, 1271 ; and that of the lately- 

 worked pit Marihaye, at Val-St.-Lambert, is 1157 feet. The 

 greatest absolute depths to which man has penetrated are 

 in mines, that are either among lofty mountains or in mount- 

 ain-valleys so much raised above the sea-level that this has 

 either not been reached at all or has only been surpassed by 

 a very small quantity. 



The Eselschacht at Kuttenberg, Bohemia, before it was 

 abondoned, had reached the enormous depth of 3545 feet 

 (Schmidt, Berggesetze, Bd. i. S. 32). At St.-Daniel, and 

 at Geist, on the Rohrerbiihel, the works, in the 16th centu- 

 ry, were 2916 feet deep. A drawing of these workings of 

 the year 1539 is still preserved. Joseph von Sperges, Ty- 

 roler Bergwerksgeschichte, S. 121. See also Humboldt, 

 Gutachten iiber Herantreibungdes Meissner StoUens indie 

 Freiberger Erzrevier, published in Herder iiber den jetzt be- 

 gonnenen Erbstollen, 1838, S. 124.) It may be imagined 

 that information of the extraordinary depth of the workings 

 at Rohrerbiihel had reached England at an early period, for 

 in Gilbert's work, De Magnete, I find the statement that 

 man had penetrated from 2400 to 3000 feet into the bowels 

 of the earth : " Exigua videtur terrae portio, quae unquam 

 hominibus spectanda emerget aut eruitur : cum profundius 

 in ejus viscera, ultra eflorescentisextremitatiscorruptelam, 

 aut propter aquas in magnis fodinis, tanquam per venas sca- 

 tarientes, aut propter agris salubrioris ad vitam operariorum 



sustinendam ncccssarii defectum, aut propter ingentes 

 sumptus ad tantos labores exantlandos, raultasque difficul- 

 tates, ad profundiores terrae partes penetrare non possumus ; 

 adeo ut quadringentas aut [<iuod rarissime] quingentas or- 

 gyasinquibusdam nietallis, descendisse, stupendus omnibus 

 videatur conatus" (Gulielmi Gilberti, Colcestrensis, de Mag- 

 nete Physiologia nova, Lond. 1600, p. 40). 



The absolute depth of the mines in the Saxon Erzgebirge 

 are 1824 and 1714 feet ; the relative depths of these respect- 

 ively are only 626 and 260 feet. The absolute depth of the 

 rich workings in Joachimsthal, Bohemia, is 1919 feet ; but 

 taking the height of the surface upon Dechen's estimate at 

 2250 feet above the level of the sea, it is obvious that there 

 the sea-level has not even been attained. In the Harz, the 

 workings in the Samson pit, at Andreasberg, are carried on 

 at the absolute depth of 2062 feet. In Old Spanish Amer- 

 ica I know of no deeper mines than those of Valenciana, 

 near Guanaxuato, Mexico : I found the Planes de San Ber- 

 nard 1582 feet deep ; but this mine does not reach the level 

 of the sea by 5592 feet. If we compare the depth of the old 

 Kuttenberg works (a depth which exceeds the height of the 

 Brocken, and only falls short of that of Etna by 200 feet) 

 with the heights of the loftiest buildings that have been 

 reared by man (the Pyramid of Cheops and the Minster at 

 Strasburg), we find that the mines are to these in the pro- 

 portion of 8 to 1. 



I have thought it important thus to bring together these 

 data in relation to the absolute and relative depths that have 

 been reached by man, a subject in connection with which 

 many errors have been constantly committed, principal- 

 ly, as it seems, through faulty reductions of the measure- 

 ments from one standard to another. On proceeding east- 

 ward from Jerusalem towards the Dead Sea, a prospect is 

 gained which, according to our present hypsometrical knowl- 

 edge, is unparalleled on the face of the earth : there, on ap- 

 proaching the chasm in which the Jordan flows, we advance, 

 in open day, along beds of rock which, according to Berton's 

 and Russegger's barometrical levellings, lie 1300 feet in 

 perpendicular depth below the level of the Mediterranean 

 Sea {vide Humboldt, Asie Centrale, t. ii. p. 323). 



95 (p. 50.) — Bason-shaped curved strata, which dip down 

 op one hand and rise again at a mea.surable distance, al- 

 though not penetrated by mines or shafts, still suffice to give 

 us accurate information of the constitution of the crust df 

 the earth at great depths from the surface. I have to thank 

 the excellent geologist M. von Dechen for the following. 

 He writes to me : " The depth of the coal measures at 

 Mont-St.-Gilles, Liege, which, with our friend M. von 

 Oeyenhausen, I have estimated at 3650 feet below the sur- 

 face, must lie at the depth of 3250 feet below the sea-level, 

 inasmuch as Mont-St.-Gilles is certainly not 400 feet high ; 

 and the coal-bason at Mons lies fully 1750 feet deeper. 

 These depressions, however, are trifling when compared 

 with that of the coal strata of the Saar River (Saarbriick). 

 After repeated trials, I have found that the lowest coal strata 

 known in the country of Duttweiler, near Bettingen, north- 

 eastward from Saarlouis, dip 19,406 and 20,656 feet under 

 the level of the sea." This conclusion exceeds by 8000 feet 

 the estimate which I have given in the text of Cosmos for 

 the bason of Devonian strata. These Belgian coal measures, 

 therefore, lie as far below the level of the sea as Chimborazo 

 rises above it, at a depth where the temperature of the eart^ 

 must be 224° C. (435° F.). From the highest summit of 

 the Himalaya to the bottom of this bason, containing the 

 vegetable remains of the primeval world, we have a perpen- 

 dicular depth of 45,000 feet, i. e. j-ij of the semi-diameter 

 of the earth. 



96 (p. 51.)— Plato, Phaedo, p. 97 (Aristot. Metaph. p. 985). 

 See Hegel, Philosophie der Geschichte, 1840, S. 16. 



97 (p. 51.) — Bessel, AUgemeine Betrachtungen iiber Grad- 

 messungennach astronomisch-geod§tischen Arbeiten, at the 

 end of Bessel und Baeyer's : Gradraessung in Ostpreussen, 

 S. 427. On the accumulation of matter on the side of the 

 moon which is turned to us, see farther, Laplace, Expos, 

 du Syst. du Monde, p. 308. 



98 (p. 51.)— Plin. ii. 68; Seneca, Nat. Quaest. Praef. c. 

 ii. " El Mundo es poco" (the earth is small) writes Colum- 

 bus from Jamaica to Queen Isabella on the 7th of June, 

 1503 ; not in the philosophical sense of the two Romans, but 

 because it seemed politic to him to represent the passage 

 from Spain as no great matter, in the same way that he 

 spoke of *' seeking the east from the west." Vide my Ex- 

 amen crit. de I'hist. de la G6ogr. du 15me siecle, t. i. p. 83, 

 and t. ii. p. 327 ; where I have, at the same time, shown 

 that the opinion maintained by Delisle, Fr6ret, and Gosse- 

 lin, according to which the extraordinary diversity in the 

 estimates of the earth's perimeter among the Greeks is 

 merely apparent, and depends on diflferences of the stadia, 

 was already advanced by Jaime Ferrer, in the year 1495, in 

 a proposal for the determination of the Papal line of demar- 

 cation. 



99 (p. 52.)— Brewster, Life of Sir Isaac Newton, 1831, p 

 162 : " The discovery of the spheroidal form of Jupiter ij 



