IN THE DEGRADATION OF THE LITHOSPHERE. 383 



destruction of the land mass. This factor is the presence of joints. 



Connected with the problems of the degradation of the litho- 

 sphere is the necessity of meeting the problems of the reduction of 

 former continental masses leaving now only residues of them as 

 islands or separated continental units such as Africa, Australia 

 and other masses believed to have been united formerly into the 

 Gondwana Land of authors.-^ 



Here also is to be included Erla, the former great continental 

 mass extending across the northern half of the globe. 



Some geologists would meet this problem by disputing in the 

 first place the existence of such continental land masses, as Gond- 

 \vana, and hold firmly to the theory of permanent ocean basins. 

 That this idea of permanent ocean basins is a widespread and deeply 

 rooted one is well enough known to need no special proof. 



We may note, however, one reference to it from one of the older 

 textbooks — thus Geikie :^'^ 



" From early geological times, the present great areas of land and sea 

 have remained on the whole where they are, and that the land consists mainly 

 of strata formed of terrestrial debris laid down at successive epochs in the 

 surrounding comparatively shallow sea." 



" Without this continent, [Eria] on the other hand, paleontologists can- 

 not explain the known distribution of Permian land life, and, further, its 

 presence is equally necessary for the interpretation of the peculiar distribu- 

 tion of marine faunas beginning certainly with Devonian and ending in the 

 Cretaceous."^! 



Connected with this is the related idea of a former worldwide 

 Mediterranean, the Tethys of Suess which extended around the 

 globe as a great encircling ocean of which the present Mediterranean 

 is a remnant. ^- 



The problem then is not one which can be dismissed by dis- 

 puting the matter in the first case because the weight of evidence 

 is against such a position, and the stability of the sea floor is an 

 hypothesis which rests more on supposition than proven fact, while 



-9 Convenient reference may be made to Pirsson and Schuchert, " Text 

 Book of Geology," Vol. 2, passim; also Suess, " Lethea Geognostica " of 

 Freeh, Paleozoicum, contains maps of Gondwana. 



30 Geikie, " Textbook of Geology," 3d ed., rev., p. 650, London, 1893. 



'1 Pirsson and Schuchert, " Textbook," Vol. 2, p. 761. 



'2 Pirsson and Schuchert, op. cit., p. 761. 



