PHYSICAL GEOGRAPHY. 299 



inclosed in the interior of the earth, the sudden change of 

 temperature of certain dense strata,* the unequal secular loss 

 of heat experienced by the crust and nucleus of the earth, 

 occasioning ridges in the solid surface, local modifications of 

 gravitation,! and as a consequence of these alterations, in the 

 curvature of a portion of the liquid element. According to 

 the views generally adopted by geognosists in the present day, 

 and which are supported by the observation of a series of well 

 attested facts, no less than by analogy with the most import- 

 ant volcanic phenomena, it would appear that the elevation of 

 continents is actual and not merely apparent or owing to 

 the configuration of the upper surface of the sea. The merit 

 of having advanced this view belongs to Leopold von Buch, 

 who first made his opinions known to the scientific world in 

 the narrative of his memorable Travels through Norway and 

 Sweden in 1806 and 18074 Whilst the whole coast of 



* De la Beche, Sections and Views illustrative of Geological Phe- 

 nomena, 1830, tab. 40; Charles Babbage, Observations on the Temple 

 of Serapis at Pozzuoli, near Naples, and on ' certain Causes which 

 may produce Geological Cycles of great extent, 1834. " If a stratum of 

 sandstone five miles in thickness, should hare its temperature raised 

 about 100, its surface would rise 25 feet. Heated beds of clay would, on 

 the contrary, occasion a sinking of the ground by their contraction ;" see 

 Bischof, Wdrmelelire des Innern unseres ErdTcorpers, s. 303, concerning 

 the calculations for the secular elevation of Sweden, on the supposition 

 of a rise by so small a quantity as 7 in a stratum of about 155,000 

 feet in thickness, and heated to a state of fusion. 



f The opinion so implicitly entertained regarding the invariability of 

 the force of gravity at any given point of the earth's surface, has in 

 some degree been controverted by the gradual rise of large portions of 

 the earth's surface. See Bessel, Ueber Maas und Gewicht, in Schu- 

 macher's Jahrbuchfur 1840, s. 134. 



t Th. ii. (1810), s. 389; see Hallstrom, in Kongl. Vetenskaps- Aca- 

 demies Eandlingar (Stockh.), 1823, p. 30; Lyell, in the Philos. 

 Trans, for 1835 ; Blom (Amtmann in Budskerud), Stat. Beschr. von 

 Norwegen, 1843, s. 89-116. If not before Von Buch's travels through 

 Scandinavia, at any rate before their publication, Playfair, in 1802, 

 in his illustrations of the Huttonian theory, 393, and according to 

 Keilhau (Om Landjordens Stigning in Norge, in the Nyt Magazine for 

 Naturvidenskabeme), and the Dane Jessen, even before the time of Play- 

 fair, had expressed the opinion that it was not the sea which was sinking, 

 but the solid land of Sweden which was rising. Their ideas, however, 

 were wholly unknown to our great geologist, and exerted no influence on 

 the progress of physical geography. Jessen, in his work, Kongeriget 

 Norge fremstillet efter dets naturlige og borgerlige Tilstand, Kjobenh., 



