REVIEWS 439 



in favor of those who consider that the earth is made of nickel-iron 

 enveloped in stony meteoritic material and kept in a rigid state by- 

 pressure. 



The author is convinced that igneous magmas are the result of the 

 fusion of shales and other sedimentary beds locally where occasional 

 rehef of pressure permits. Such relief is explained in two ways — the 

 rising of a competent stratum in an anticline, and under uplifted fault- 

 blocks. He argues that laccoKths are of this origin. Apparently batho- 

 liths are merely enlarged or coalesced laccoliths. He regards these domes 

 as the initial stage in the forming of large anticlines and supposes that 

 the Colorado-Montana region affords proof of the theory. To this end 

 he is obliged to redate the pre-Cambrian granites of the anticlinal cores 

 and put them in the late Cretaceous; but unfortunately the field facts 

 are conclusively against him. 



As to the mode of egress of magma thus formed, he agrees with Daly 

 that blowpiping by gases and vapors which collect at the crown of the 

 laccolith, is the chief process. These gases are not "juvenile" but are 

 acquired from the shales fused and from rocks invaded during the ascent. 



Turning to the general deformation of the earth, the author not only 

 accepts the tetrahedral theory, of which the book gives a good summary, 

 but he adds a novel modification of it, whereby the earth is supposed to 

 have developed a twinning along a plane following the ancient Sea of 

 Tethys. This left the hypothetical Paleozoic continents of Atlantis and 

 Gondwana protruding to the north and south. Why this twinning did 

 not affect the earth in earlier and modern times is not explained. The 

 author ridicules those timid persons who suspect the existence of narrow 

 land bridges from continent to continent in earlier periods in order to 

 account for the strange distribution of faunas and floras past and present, 

 and favors the bolder idea that the existing ocean basins have been made 

 in la,rge part by the collapse of the Permian continents, especially in the 

 Atlantic and Indian regions. 



The mountain arcs of southeastern Asia are interpreted as young 

 anticlines — not overthrust from the land, as Suess presumed, but under- 

 thrust from the ocean basins. In this he seems not to have been aware 

 of the earlier writings of Chamberlin and others regarding the sinking 

 of the oceanic sectors resulting in the crowding of the continental borders. 

 His argument is by no means convincing, and the experimental illustra- 

 tion fails because the photograph of the apparatus is not clear. 



The forms of the arcs in plan are then discussed, but if there is in the 

 chapter anything deserving to be called an explanation, the reviewer has 



