THE GEOLOGICAL EVIDENCES. 49 



folded mountains. To estimate the result comparison may be made with 

 estimates of the amount of crustal shortening involved in the formation 

 of folded mountains. It is obvious that the estimates which assign the 

 greatest amount of shortening to given amounts of folding are those which 

 would give the least mountain production to the sinking of the equatorial 

 belt in question and are hence the most conservative. One of the highest 

 estimates of the crustal shortening involved in the formation of a familiar 

 range of mountains, made by a competent geologist on the basis of much 

 personal field work, is that of Professor Albrecht Heim for the formation 

 of the Alps, which is 74 miles. Somewhat comparable estimates are those 

 of Dr. Peter Lesley for the folds of the Appalachians west of Harrisburg, 

 which is 40 miles, and that of Dr. G. M. Dawson for the Laramide Range 

 in British Columbia, which is 25 miles. In the opinion of some other geol- 

 ogists these estimates are too high. If therefore we apply these to the 

 equatorial belt the results will be relatively conservative. If we use Heim's 

 figure, the sinking of the equatorial belt to the assigned amount should 

 give 15 mountain ranges of the magnitude of the Alps standing across the 

 equator. They should be short ranges dying away within 35° of latitude 

 on either side. If we apply Lesley's estimate there should be 28 ranges of 

 the order of the Pennsylvanian Appalachians standing across the equator; 

 if the estimate of Dawson be used, there should be 45 ranges of the magni- 

 tude of the Laramides of British Columbia. 



If we start with the 4.03-hour rotation-period instead of the 3.82-hour 

 period, these figures become, 13, 25, and 40, respectively; and they may 

 be easily reduced for later periods. 



If, as an alternative, we choose to assign more mashing of the shell and 

 less corrugation, it will merely give us a massive equatorial ridge with less 

 cross-folding. If, as another alternative, we choose to assign more com- 

 pression into denser rock, we shall have greater resistance to subsequent 

 erosion and higher specific gravities to account for. 



Under no tenable hypothesis, so far as I can see, can an equatorial 

 protuberance of 180 miles comparable to the 3.82-hour period, or of 160 

 miles comparable to the 4.03 period, or of 87 miles comparable to the 5.35- 

 hour period be assumed to have subsided to the present equatorial dimen- 

 sions without having left a distinct record of itself in the form of transverse 

 ranges of mountains, or of irregular protrusions, or of indurated terranes, 

 or of some combination of these or of the other modes in which exceptional 

 tangential stress is accustomed to express itself in the shell of the earth. 



It is to be noted that, by the terms of the retardational hypothesis, 

 the tangential stress must have been applied constantly from the beginning 

 to the present time. It was indeed more rapidly applied in the earlier 

 stages, but some stress has been added constantly ever since. If compres- 

 sion to a more compact form is to be assigned at all, in any important 

 degree, it must be assigned to the first stages of stress, and the later pro- 

 trusions would be all the more enduring on account of this early induration. 



Now it is for every one to examine for himself the equatorial tract to 

 see if it presents the character which the hypothesis requires. For myself, 

 I am quite unable to find it. There is not even an equatorial belt of land, 



