OROGENY AND EARTH’S ROTATION 
59 
example, in the Appalachians where the American geologists 
' mainly worked. The two phenomena are not necessarily inti¬ 
mately dependent. Neither is the coincidence so genetically com¬ 
plete as Hall and Dana believed. There is, indeed, now simpler 
explanation of Appalachian tectonics. It has the great advantage 
of not being open to the many basic objections raised against the 
Reade idea. ^ 
The Reade modification of the Huttonian conception of moun¬ 
tain-building on account of regional rock-expansion through heat¬ 
ing is not nearly so revolutionary, nor so notably different in its 
effects from other conceptions, as might at first blush appear. 
Theoretically, of course, the force of expansion acts in all direc¬ 
tions, just as Reade so ably argues, but because of the fact of 
tremendous resistance in all directions, except upwards or out¬ 
wards, actual and appreciable movement is in the latter direction 
mainly, if not solely. So there is really, in the finality of the 
case, little to choose between in the three-dimension hypothesis, 
as formulated by Reade, and the earlier linear idea, as discussed 
by Hutton, Babbage, Lyell and Dana. 
Anticipating somewhat certain fatal shortcomings of the expan¬ 
sion hypothesis both Hall and Dana, by seeking refuge in the as¬ 
sumption that mountains are formed only where there are exces¬ 
sive accumulations of sediments, raise the question whether ex¬ 
pansive effects do not have severe limitations. By this position 
these authors seemed especially well fortified so far as the up¬ 
heavals with which they were most familiar were concerned. 
Reade, recognizing the force of the argument, also sets out from 
the same starting point. Although the association does not ap¬ 
pear to hold good in many other areas it may prove universal in 
its application, but if so it is for other reasons than those generally 
advanced. 
On the whole, Reade’s three-dimension hypothesis complicates 
rather than explains the situation. Areas of noteworthy sedi¬ 
mentation are more or less basinal in form; they are circular in 
outline. Accordingly, three-dimension expansion should produce 
great dome-shaped elevations. There should be no long narrow 
plications such as characterize the large majority of mountain 
districts. The term mountain range itself implies linear develop¬ 
ment. Mountain extension in one direction is usually many times 
