66 o. E. SCHI0TZ. [NORW. POL. EXP. 



, 



fM, dw L dh = f j R* do, L dh = 



00 



f 1 



= 0! R* dw\Q l dh, 



and under the oceans to 



.-*. 



t .R? dw ( L dfe -f- dfe). 



o A, -A, 



These two pressures are not equally great, and their difference 4, 



-*- * 



i-<>)dh+\( 9 t -l)dh], II. 



o , -* 



must, as we shall immediately see, be negative. In order to produce the 

 distribution of matter in the earth's crust, that is found beneath the portions 

 of continent under consideration, from the distribution of matter that exists 

 beneath the oceans, masses must be removed from the deeper strata, and 

 added above, where the sea is found; and in this way the attraction exerted 

 by the interior nucleus upon the masses, and consequently their pressure 

 upon it, are diminished. The sum of the two integrals in II, must thus, as 

 already mentioned, be negative. 



It is easy to find an approximate value for this sum, and thus for the 

 difference in pressure, J, even if nothing more is known as to how the 

 density changes down a vertical line from the surface. If we call the sum 

 of the integrals 6, we may put 



where Q' indicates the difference between the mean values of the densities 

 (>, and Q in the crust reaching from h to h = h^ % 2 , and / is the 

 average density in the uppermost stratum of continent of thickness h t . 

 According to equation I., we now have, neglecting quantities of the second 

 order, 



[ (p, i P) (h h\) dh -f- (PI 1) (h h,\ dh] = 0. IV. 



A, -A, 



