374 Revieios — Capt. C. E. Button — 



of unstable equilibrium assumed, a large extent of crust would divide 

 and subdivide itself, until the fragments were small enough, to give 

 an appreciable value to their coherence. The directions of the lines 

 of fracture would be determined by the inequalities of the distribu- 

 tion of deposit. The problem thus becomes a hydrostatic one. The 

 axes of maximum deposit become the axes of future synclinals, and the 

 axes of minimum deposit mark the positions of future anticlinals. 

 The heaviest portions sink into the lighter colloid mass beneath, pro- 

 truding it laterally under the lighter portions, where by its lighter 

 density it tends to accumulate. These movements are the plainest 

 sequences of well-known hydrostatic laws, which we cannot hesitate 

 to accept if we accept the premisses. The resulting movements would 

 be determined, first by the amount of difference in the densities of 

 the upper and lower masses, and secondly by inequalities in the 

 thickness of the strata. The forces now become adequate to the 

 building of mountains, and the plications of strata ; and their modes 

 of operation agree with the classes of facts already set forth as the 

 concomitants of those features. Such is Captain Button's theory, 

 which he next proceeds to apply to plications — to "mountain build- 

 ing " — and to volcanos. 



When once indicated, iiie consequences of this theory can be 

 followed out by the geological thinker ; but at the risk of tedious- 

 ness it seems but right to relate the author's own application of it in 

 the more important eases. 



Wherever loads of sediment become heaviest, there they sink 

 deepest, protruding the colloid magma beneath them to the adjoining 

 areas which are less heavily weighted, forming at once both syn- 

 clinals and anticlinals. The disturbance would be in proportion to 

 the difference of densities of the upper and lower portions, and to 

 the plasticity of the latter. Hence would arise (1) low undulations, 

 which occur where the bedding is less unequal ; (2) larger features, 

 as in the Jura and Appalachians, where heavy beds of deposit have 

 accumulated rapidly in long and narrow belts. These have subsided, 

 forming troughs, in which the sediments have continued to gather, 

 and augment the disturbing cause. The material displaced by the 

 sinking masses must have been driven beneath the anticlinals, turn- 

 ing up their edges with increasing inclination, and pushing up higher 

 the strata above them. In this position the two branches of the 

 inclined strata form great top-heavy masses, with a powerful ten- 

 dency to greater inclination ; and the great blocks may even become 

 inverted. By the theory he also seeks to explain the fact, that the 

 steeper inclination of the dips in the coast-range of California, and 

 in the Appalachians, is from the area of chief deposit towards what 

 was the lightened land, from whose denudation the materials were 

 derived. (3) We have mountain building. All typical mountains, 

 consisting of granitoid cores protruded through strata, and towering 

 above them, stand upon lofty tables. Such mountains are quite 

 unknown in low countries, being a series of sharp pinnacles and 

 ridges planted upon a broad expanse of high lands. The uplifting of 

 the regional belts [of high land] on which they occur, by columnar 



