IN THE DEGRADATION OF THE LITHOSPHERE. 381 



land surface is not however to be explained by ordinary land ero- 

 sion, nor does marine erosion explain it any more easily unless 

 there be entertained at the same time the conception of some struc- 

 ture such as the joint segments here discussed. Steep cliffs and 

 deep fjords do not per force mean a sunken coast line primarily, 

 they may be I conceive land or rock shapes due essentially to great 

 joint lines. 



That there exists observed evidence for believing in the ability 

 of a jointed structure to induce a breaking down and destruction 

 of plateaux is shown by the investigations of E. Erdmann and 

 Nathorst.-" These investigations were carried out in the struc- 

 tvires of Scania, an old province in southern Scandinavia and in the 

 opinion of so able a critic as Suess justify the opinion that 



"Scania is formed of fragments of a great plateau broken by joints. ... As 

 E. Erdmann has shown the whole region is traversed by great longitudinal 

 fractures which run from northwest to southeast ; along these the whole 

 country has been let down irregularly with the formation of troughs and 

 horsts." 



The investigations of Nathorst have shown further that this sub- 

 sidence has taken place at different times, 



" and that it is possible to classify the fractures according to their age. . . . 

 In this country which has not been subjected to any folding since the Cam- 

 brian period we have a new and instructive example of the breaking down 

 of a tableland accomplished piece by piece." (Suess, op. cit., Vol. 2, p. 48.) 



Some of the fractures present have been determined by Nathorst 

 as older than the Trias. 



There exists then more than simply hypothetical ground for 

 considering jointing as one of the great fundamental shaping factors 

 of the earth. The essential unity of the great mass of the upper 

 portion of the northern hemisphere will probably be shown more 

 and more as stratigraphic investigation on both the continents of 

 Europe and America proceeds. This unity is already shown how- 

 ever in the similarity of structures now to be observed over widely 

 separated areas, in the analogies if not actual parallelisms along 

 the northern coasts and arctic lands where marine denudation is 



28 See citations given earlier in this paper. Their studies are reviewed by 

 Suess in Vol. 2 of the English edition of " The Face of the Earth," 1906, 

 pp. 46 ff. 



