312 Doubts Relative to the Epochal and 



that the atmosphere is the same now as then, and that its 

 amount of aqueous vapour be constant, and so the effect of 

 the chemical or calorific rays of the sun were brought into 

 action then as at the present time. 



The slow decrease in the eccentricity of the earth's orbit 

 ought also to be borne in mind, as a further source of dimi- 

 nished solar heat.* 



Should it be said, on the one hand, in opposition to the 

 aforesaid conditions of increased superficial area and dimi- 

 nished heat, that such increased area is merely fractional 

 in relation to the diameter of the earth, it ought, on the 

 other hand, to be remembered, that the diminution of solar 

 heat, as determined by positive data, is merely fractional, 

 though it is well proved. 



2ndly: Let it be granted that the space included between 

 the two circles, " ut, out, out," and " in, in, in," represent 

 the solid crust of the earth, as set forth in the accompanying 

 diagram ; and let A, B, C, be an equilateral triangle, whose 

 base shall extend from B to C, and whose apex shall be A. 

 If, then, force be acting equally in all directions, as from the 

 inner circle of the earth's crust, " in, in, in," which inner 

 circle forms the outer boundary of a great caldron, and at the 

 point A the crust shall yield, then the lines F F F will re- 

 present the direction of force from the circumference to 

 the sides of the triangle, and the equilateral triangle ABC 

 will give the widest base conceivable, in the straight line 

 B C, in which it is possible that force, effecting a rupture 

 at the point A, through the earth's crust to the point P, can 

 attain. 



After making all due allowance for the thickness of the 

 sides of the mass elevated upon the earth's surface from 

 such a base to the height of five to ten miles, it is impossible 



* Vide Sir J. Herschel's " Discourse on the Study of Natural Philo- 

 sophy," 1831, p. 147. 



