62 Mr. Mauter on the Dynamics of Earthquakes. 
This is but a very incomplete sketch, however, of what takes place ; for, 
besides the wave analogous to a tidal wave produced and propagated on the sur- 
face of the ocean, a second wave (of sound namely) will be propagated through 
the mass of the ocean water likewise, with a velocity far greater than the former, 
and will reach the land, and be heard there as a sound long before the great sur- 
face wave will have rolled in. The terrestrial sound wave is isochronous with 
the great elastic wave or earth wave of shock. 
Referring to the internal mechanism of a fluid wave, as experimentally 
observed by the Webers,* (see Plate II. Fig. 1), it is not yet known that pre- 
cisely analogous motions take place amongst the particles of solids within their 
limits of elasticity, when transmitting a wave of the first order; but it seems 
highly probably that there is a close analogy in the motions of the particles in 
both cases, so that the particles of a table land of solid rock, transmitting an 
elastic wave, or earthquake shock, from a distant primary impulse, do, in all pro- 
bability, describe similar elliptic curves to those of a watery wave, and varying in 
the same way with respect to depth, though much smaller, because withheld 
within the elastic limits due to the particular rocky mass or masses, and trans- 
mitted also with inconceivably greater velocity. This, however, is certain, that 
the swrface of the solid earth does undulate ; it has been repeatedly observed to 
do so. The transit of the wave along the surface, even, has been observed, as 
in the great earthquake of Jamaica, in 1692: hence, it is certain that any par- 
ticle upon the surface of the earth, under such circumstances, must describe 
either a circle or an ellipse, most probably the latter, whether those within the 
mass of the undulating land do so or not. 
Difficult as it may seem at first to reconcile to our common notions of solid 
bodies, that such internal motions should pass through them, causing compression 
or even intermobility of their particles within their elastic limits, yet, through 
large measurable spaces, and with immense velocity, such motions are, in fact, 
before us constantly: the vibrations of the air of a drawing-room shake the solid 
walls of the house, when a tune is played upon a piano-forte, or otherwise the 
tune could not be heard in an adjoining house. Captain Kater found that he 
could not perform his experiments upon the length of the second’s pendulum any 
* Wellenlehre, auf experimente gedriindet. 
