12 Rev. 0. Fisher on the Surface Elevations and other 



Then 



and 



Hence 0*02 is too small a value for x. 



Try x = 0-03; then 



p = -0-94933, 



and ? = 0-856236. 



Consequently this value of x is too large, and x must lie be- 

 tween U-02 and 0'03. 



Treating p and q as the ordinates of two curves, the value 

 of x sought is the abscissa at their intersection, and, if that is 

 O03— Bx, Bx will be given by 



8x= P + q 



dp + dq> 



dx dx 

 without regard to signs. 

 l$ov? log p = log \±[(r-x)' 2 + l]-l(r-xy X \ -\ogre*\ 

 dp 

 . g; -( r -x)+ (r-x) 2 x-±(r-xf re^2x 

 p - %[(r-xY +\-\-±{r-xYx re* ' 



When x = O03 this gives 



*=-894. 

 dx 



Also rf? = e _ x2 = eH ^- 9 =0 . 99910 . 



dx ' 



whence 



^ P+ ^ 

 dp dq 



dx dx 



And tf = O03 -O00202 = 0-0280 in terms of a as the unit. 

 This is correct to the number of places given. 



Now a at the present time is, on the supposition that the 

 temperature of solidification was 7000° F., 402832 feet. The 

 level of no strain is therefore at present at a depth of 11 27i) 

 feet, or 2-1361 miles. 



To find x approximately from the equation 

 e -Z{ (r-xY a* _ {r-xfx ) C* * 



"J. •"*"*• "Jr *"**■■ 



