CarruTHEers.—Retardation of Earth’s Rotation by Volcanic Action. 868 
they clash together. The molecular motion travels to the same distance in 
both; but in the western mass, the blow was administered in the opposite 
direction to that in which the mass was moving, and the greater part of its 
energy is converted into heat, close to the line of fracture, leaving only a small 
part to be carried on and distributed over the rest of the distance to which 
the action extends. The expansion depends on the heat evolved, so that 
it would nearly all take place close to where the blow was administered. 
With the eastern mass the heat would be carried on more uniformly, 
giving a more gentle slope to the hills. 
By the hypothesis, earthquakes and all the other sensible effects of 
elevation are quite superficial, extending only a few miles in depth. The 
great primary movement would be quite unfelt if the outer part of the 
crust were flexible. It is only the surface crushings and fractures which 
are felt. 
This agrees with the observations of Mr. Mallet, who, from calculations 
founded on the direction in which the shock was felt by observers at some 
distance apart, has deduced the depth at which the jar was given in 
different earthquakes. Quoting from memory, and at second hand, I 
believe he states this to be not greater than 80 miles. 
The elevation of a mountain chain does not add more matter to that 
part of the earth where it occurs; the matter which was there before is 
expanded, and thus has less specific gravity than the rest of the earth’s 
crust. In the case of a great range like the Himalayas this loss of specific 
gravity might become sensible, and it has been found that this really is 
the case. The earth under the Himalayas has less specific gravity than 
elsewhere. 
My hypothesis requires that there should be a tendency towards volcanic 
action along the flanks of lines of elevation, at a considerable distance from 
the latter. To show that this agrees with observation, I will quote from 
Scrope’s work on Volcanoes, to which I am indebted for most of the facts 
recorded below :— 
‘In the body of this work it was stated that a more or less distinct 
parallelism, or coincidence, is traceable between the leading mountain 
chains of the two hemispheres and the linear bands of volcanic vents, 
active or extinct, insular or continental, by which they are traversed.”’ 
And again, after describing the great east and west line of elevation, 
extending from the north-west of Spain to China, he says :— 
‘** Now, it is the fact that these several mountain chains are bordered 
at moderate distances, on one or both sides, by linear bands of rocks of 
yoleanic formation, along which therefore eruptions have, at some time or 
other, taken place.” 
