Rene/vs — T. Mellard Reach — Earth Structure. 81 



folding and permanent ridging-up and corrugations of the earth's 

 surface." These movements, it is hekl, may be initiated by a long 

 course of sedimentation, causing a sinking of the sea-bed. 



In connection with this subject the author points out that 

 " a depression of the ocean bottom will draw the waters from the 

 land and increase the land areas, while a rise of the sea-bed will 

 cause a transgression of the oceanic water over the land." Here 

 it may be remarked that in 1868 Mr. H. B. Medlicott observed that 

 " The assumption of the absolute permanence of the sea-level (that 

 its level has permanently maintained the same radial distance from 

 the centre of the earth) has quietly taken the position almost of 

 a postulate in geological induction. The notion is inconsistent with 

 any progressionist doctrine, essentially so with Laplace's theory." ' 

 Mr. Mellard Reade. however, sees no evidence of enormous con- 

 traction of the earth's I'adius, although he observes that " in every 

 known instance where proof is possible, the continents are at lower 

 levels now with respect to the sea than they were on some former 

 occasions during their lengthened history." The explanation given 

 in these cases is that there has been a rise of portions of the floor 

 of the ocean basins. 



After referring to the persistence of certain lithologic characters in 

 formations over wide areas, notably among the Carboniferous, Triassic, 

 and Oolitic groups, the author remarks that the land areas grow 

 by accretion from existing land, the ruins of former continents 

 having added to their extent, and thereby securing the continuity 

 of land areas throughout geologic time. That " New lands are the 

 consequents of sedimentary loading and recurrent expansion" is 

 a subject he dealt with in his " Origin of Mountain Ranges." 



Turning to the sub-oceanic configuration, the author gives reasons 

 for believing that the bed of the Atlantic is not a plain, " but 

 a diversified surface like that of the dry land, and that a large 

 portion of it has at some former geological age been carved out by 

 sub-aerial agencies." These diversified contours lie beyond the 

 continental shelves, which are mainly sedimentary. 



In Book ii the author discusses the dynamics of mountain structure 

 and experimental geology, a subject more fully treated in his work 

 on the "Origin of Mountain Ranges." Herein he brings to bear 

 his experience as an architect and engineer, and the practical 

 experiments he has made combine to give weight to his conclusions. 

 The results of experiments are depicted in numerous plates, illus- 

 trating compression, shearing, and contortion of various kinds. 

 Microscopic sections of rocks are also given. The time has perhaps 

 long passed when anyone would sympathize with Ramsay, who 

 (in 1877), while A. Geikie and J. Clifton Ward were examining 

 thin slices of rock under the microscope, exclaimed, " I cannot see 

 of what use these slides can be to a field-man. I don't believe in 

 looking at a mountain with a microscope." ^ 



1 Quart. Journ. Geol. Soc, vol. xxiv, p. 37. 



' "Memoir of Sir A. C. Eamsay," by Sir A. Geikie, 1895, p. 343. 



DECADE V. — VOL, I. — NO, II. (> 



