94 Mattet on the Dynamics of Earthquakes. 
experiments upon different specimens from every known formation of rock, in 
order to get the average result for each formation,—and when, in addition, 
the actual time of transit of the great earth wave or earthquake shock shall have 
been accurately observed, over long ranges, in various formations, and with suit- 
able instruments and precautions, then shall we be in a position not only fully to 
verify the truth of this theory of earthquake motion, but able also to deliver 
into the grasp of the computist, a wide domain of physical geology, hitherto 
én unprofitable waste of uncertainty and conjecture. 
We may notice a few of the more direct applications to geology which 
may be made of our theory, whenever such data are obtained. 
However well modern geologists have surveyed and mapped the formations 
constituting the land which we can see and handle, of the nature of the bottom 
of the great ocean we know nothing; no human eye ever has or ever can behold 
it; we cannot even reach its deep abysses with the sounding line; yet the ocean 
covers nearly three-fourths of our entire globe, and of this vast area the geology 
is an utter blank. If, however, we are enabled hereafter to determine accu- 
rately the time of earthquake shocks, in their passage from land to land, under 
the ocean bed, we shall be enabled almost with certainty to know the sort of 
rock formation through which they have passed, and hence to trace out at least 
approximate geological maps of the floor of the ocean. For, knowing the time 
of transit of the wave, we can find the modulus of elasticity which corresponds 
to it, and finding this, discover the particular species of rock formation to which 
this specific elasticity belongs. 
It is needless to enlarge upon the value to geology of even a very general 
knowledge of the nature of the great ocean beds. Perhaps no single circumstance 
has more retarded our forming distinct perceptions of the great changes, hourly 
occurring, as to the forms and boundaries of sea and land, or which have, at past 
epochs, taken place, than the impossibility of seeing the geological map of the 
world asa whole. The land, or rather a few fragments of the land, alone, we 
have seen, the ocean shrouds the vast remainder; and the imagination can no 
more seize the traces of successive cataclysms, or of the slow but ever-acting 
agencies, by which our globe has been changed and remodelled, by this partial 
and imperfect glimpse, than the statuary could judge of the proportions of the 
muffled figure that presented but part of a single limb to his view. 
