1899 — 1900.1 Lord Kelvin on the Motion in an Elastic Solid. 223 
•90 
•80 
■95- 
■ 70 - 
•60 
■50 
•4-0 
•30 
Fig. 1. 
•00 
•95 
•90 
•80 
densities of the ether at (not the average density of the ether 
within) the concentric spheri- j.00 
cal surfaces of radius r in -00 
the atom. Column 5 in 
each table shows l line of ‘90 
the excess (positive or nega- -95 
tive) of the quantity of 
ether in a shell of radius *80 
r and infinitely small thick- 
ness e as disturbed by the 
atom above the quantity in 
a shell of the same dimen- 
sions of undisturbed ether. 
The formula of col. 2 makes 
r = 1 when r —1 ; that is 
to say, the total quantity 
of the disturbed ether within 
the radius of the atom is 
the same as that of undis- 
turbed ether in a sphere of 
the same radius. Hence the 
sum of the quantities of 
ether calculated from col. 5 *70 
for consecutive values of r, 
with infinitely small differ- 
ences from r = 0 to r= 1, °60 
must be zero. Without cal- 
culating for smaller differ- 
ences of r than those shown * 50 
in either of the tables, we 
find a close verification of 
this result by drawing, as 
in fig. 2, a curve to repre- 
sent ( p - 1 )r 2 through the 
points for which the value 
is given in one or other of 
the tables, and measuring 
the areas on the positive and negative sides of the line of 
•70 
•63 
•50 
