STRUCTURE OF DEFORMED MARBLE. 815 



that there may have been a deposition of infinitesimal amounts of calcium 

 carbonate along very minute cracks or fissures, thus contributing to 

 maintain the strength of the rock. No signs of such deposition, however, 

 are visible."" 



It has been pointed out in another place (see pp. 747—748) that the 

 greater strength of this sample, as compared with those in which water 

 was not present, is almost conclusive proof that solution and deposition, 

 or recrystallization, did take place to some extent, 



Adams and Nicolson compare the structures produced in the Carrara 

 marble artificially deformed with limestones and marbles in various regions 

 where the rocks have been metamorphosed under deep-seated conditions. 

 In 21 rocks from different regions, 10 of which are marble and 11 of which 

 are limestones, they find all the structures which they have artificially pro- 

 duced to be paralleled.'' But an equal number of rocks from other regions, 

 only 3 of which are limestones, 2 dolomites, and 16 marbles/ which, as 

 shown by the greater number of marbles, have undergone more profound 

 metamorphism, they say "do not present any undoubted evidence of 

 movement under pressure. Their structure is that of a mosaic, apparently 

 resulting in each case from the recrystallization of a previously existing 

 finer-grained limestone. This process, as described by Lepsius in the Attic 

 marbles/ consists of the enlargement or growth of certain of the constit- 

 uent grains at the expense of others until finally a coarse-grained mosaic is 

 produced." 6 In these instances it is apparent that recrystallization is the 

 dominant process, for only by this process can large individuals be produced 

 by the merging of small ones. (See Chapter VIII, pp. 690-696.) Adams 

 and Nicolson conclude: "While, therefore, recrystallization undoubtedly 

 plays an important, and in many cases probably a chief part, in the great 

 movements which are observed to have taken place in the limestones of 

 contorted districts, this process is by no means the only one b}^ which such 

 movements are brought about. Many limestones under pressure in the 

 earth's crust flow precisely as metals do, by deformation of the com- 



" Adams and Nicolson, cit., p. 385. 

 » Op. cit., pp. 387-390. 

 ''Op. cit., pp. 389-390; Nos. 22-42. 



d Lepsius, B., Geologie von Attika; em Beitrage zur Lehre vom Metamorphismus der Gesteine, 

 Dietrich Riemer, Berlin, 1896, p. 186. 

 e Adams and Nicolson, cit., p. 397. 



