TERRESTRIAL PHENOMENA. 151 



they contain, must lie, as, for instance, in Belgium, more than 

 five or six thousand feet* below the present level of the sea ; 

 and that the calcareous and the curved strata of the Devonian 

 basin penetrate twice that depth. If we compare these sub- 

 terranean basins with the summits of mountains that have 

 hitherto been considered as the most elevated portions of the 

 raised crust of the Earth, we obtain a distance of 37,000 feet 

 (about seven miles), that is about the g-yjth of the Earth's 

 radius. These, therefore, would be the limits of vertical depth 

 and of the superposition of mineral strata, to which geognos- 

 tical inquiry could penetrate, even if the general elevation of 

 the upper surface of the earth were equal to the height of the 

 Dhawalagiri in the Himalaya, or of the Sorata in Bolivia. 

 All that lies at a greater depth below the level of the sea than 

 the shafts or the basins of which I have spoken, the limits to 

 which man's labours have penetrated, or than the depths to 

 which the sea has in some few instances been sounded, (Sir 

 James Ross was unable to find bottom with 27,600 feet of 

 line,) is as much unknown to us as the interior of the other 



* Basin-shaped curved strata, which dip and reappear at measure- 

 able 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, con- 

 sequently, a great geognostic interest. I am indebted to that excellent 

 geognosist, Von Dechen, for the following observations. "The depth of 

 the coal-basin of Liege, at Mont St. Gilles, which I, in conjunction with 

 our friend Von Oeynhausen, have ascertained to be 3890 feet below the 

 surface, extends 3464 feet below the surface of the sea, for the absolute 

 height of Mont St. Gilles certainly does not much exceed 400 feet ; the 

 coal-basin of Mons is fully 1865 feet deeper. But all these depths are 

 trifling compared with those which are presented by the coal- strata of 

 Saar-Revier (Saarbriicken). I have found, after repeated examinations, 

 that the lowest coal-stratum which is known in the neighbourhood of 

 Duttweiler, near Bettingen, north-east of Saarlouis, must descend to 

 depths of 20,682 and 22,015 feet (or 3'6 geographical miles) below the 

 level of the sea." This result exceeds, by more than 8000 feet, the 

 assumption made in the text regarding the basin of the Devonian strata. 

 This coal-field is therefore sunk as far below the surface of the sea, as 

 Chimborazo is elevated above it : at a depth at which the earth's tempe- 

 rature must be as high as 435 F. Hence, from the highest pinnacles of 

 the Himalaya to the lowest basins containing the vegetation of an earlier 

 world, there is a vertical distance of about 48,000 feet, or of the 435th 

 part of the Earth's radius. 



