NOTES. 



xli 



which I am acquainted is the Valeuciana, near Guanaxuato in Mexico, where 

 I found the absolute depth of the Planes de San Bernardo 1582 (1686 Ene;.) 

 feet; but this is still 5592 (5960 Eng.) feet above the level of the sea. If 

 we compare the depth of the Kuttenberger mine (a depth greater than tha 

 height of the Brocken, and only 200 feet less than the height of Vesuvius, 

 with the loftiest buildings erected by man, with the Pyramid of Cheops and 

 with the Cathedral of Strasburg, we find the proportion of 8 to 1. Our geo- 

 logical writings contain so many statements either vague or disfigured by 

 erroneous reduction to Parisian feet, that I have thought it desirable to bring 

 together in this note all the certain information which I could collect respect- 

 ing the greatest absolute and relative depths of artificial excavations. In 

 descending eastward from Jerusalem to the Dead Sea and the valley of the 

 Jordan, a view is enjoyed which, according to our present hypsometric 

 knowledge of the surface of the earth, has no parallel in any other region. 

 The rocks on which the traveller treads, with the open sky over his head, are. 

 according to the barometric measurements of Berton and Riissegger, 1300 

 (1388 Engl.) feet below the level of the Mediterranean. (Humboldt, Asie 

 centrale, T. ii. p. 323.) 



( l25 ) p. 150. Basin-shaped strata, which sink and reappear at distances 

 which can be measured, although their deepest portions may be inaccessible 

 to the miner, yet afford sensible evidence of the constitution of the crust of 

 the earth at great depths beneath the surface. Facts of this kind possess, 

 therefore, great geological interest : I am indebted to the excellent geologist 

 Herr von Dechen for those subjoined : " The depth of the Liege coal basin 

 at Mont-St.-Gilles I infer, from the joint investigation of our friend Herr von 

 Oeynhausen and myself, to be 3650 feet (3809 Engl.) below the surface, or 

 3250 (3464 Engl.) feet below the level of the sea, the elevation of Mont- 

 St.-Gilles being certainly under 400 Trench feet ; the coal basin of Mont 

 must be fully 1750 (1865 Engl.) feet deeper still. But all these depths are 

 small compared to that which may be deduced from the superposition of the 

 coal strata of the Saar-Revier (Saarbriicken). I infer from repeated surveys 

 that the lowest coal strata which we know in the district of Duttweiler, near 

 Bettingen, north-east of Saarlouis, descend to a depth of 19406 (20682 Eng.) 

 and 20656 (21358 Engl.) feet below the level of the sea, or 3.6 geographical 

 miles." This result exceeds by 8000 (8526 Eng.) feet the assumption made 

 in the text for the depth of the basin of the devonian strata : it is a depth 

 below the level of the sea equal to the height of the Chimborazo above it, and 

 at which we should infer the temperature to be as high as 224 Cent. (467" 



