igos.j THE PHYSICS OF THE EARTH. 221 



Excluding from consideration the crystalline belt on the east, 

 Claypole estimated the shortening of the Appalachians in Pennsyl- 

 vania at 46 miles. In the same way McConnell estimated that of 

 the Laramide range in British America at 25 miles, and Leconte 

 that of the Coast Range in California at from 9 to 12 miles. Cor- 

 responding estimates have been made for many other mountain 

 ranges ; but, for reasons already given in dealing with the origin 

 of the Swiss Alps, § 28, these estimates are too large. The crust 

 was broken apart at both top and bottom when the ranges were in 

 the sea, and the folds heretofore assumed to be complete were 

 never really so. Consequently no slack in the earth's crust is re- 

 quired to explain these folds ; it was never loose from the globe and 

 never moved horizontally, except when forced by earthquake move- 

 ments proceeding from the underlying trenches in the sea bottom. 



The undermining and folding of the crust has given the Ap- 

 palachian Mountains in many places the aspect of a series of immense 

 billows, running parallel, as if swept in by a vast disturbance of 

 the sea. But not even seismic sea waves of the most imposing 

 magnitude could approach the size of these gigantic folds, the origin 

 of which heretofore has been so mysterious. The finding of a simple 

 and natural explanation of tJicsc great billozvs of the land will be 

 scarcely less interesting than the discovery of the cause of seismic 

 sea waves. Both depend on earthquakes, though in very different 

 ways. The land billows are cumulative products of an infinite series 

 of seismic disturbances along the margin of the sea; the seismic 

 waves are small in comparison, and result from a single disturbance 

 of the sea bottom, made in process of shaping the vast billows of the 

 land, which in all generations have appealed to the imagination of 

 the painter, poet, and student of nature. 



§ 31. Analogy Betzveen the Uplift of the Islands of Japan by the 

 Movement from the Tuscarora Deep and of the Plateau of Tibet 

 from the Indian Ocean. — The uplift of the Islands of Japan now 

 going on by the expulsions of lava from beneath the Tuscarora Deep 

 is proved by the terrible earthquakes and seismic sea waves afflict- 

 ing that region, as well as by the historical fact that the east coast 

 of Japan is known to be rising from the sea. Perhaps in general 

 the movement is slow and insensible, but occasionally earthquakes 



PROC. AMER. PHIL. SOC. .\LVII. 189 O, PRINTED SEPTEMBER 23, I908 



