Page:Great Neapolitan Earthquake of 1857 Vol 2.djvu/231

170 {| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;" ! scope="col" style="width: 250px;" | ! scope="col" style="width: 20px;" |
 * 1853
 * 270·40
 * 1854 || 141·90
 * 1855 || 90·20
 * 1856 || 186·25
 * 1857
 * 11·30
 * }
 * 1856 || 186·25
 * 1857
 * 11·30
 * }
 * }

or, as compared with the mean for the month of the preceding four years, only as 11·3 inches to 172·19 inches, or less than one-fifteenth of the usual quantity.

Admitting, as we must, the identity of the explosive power at the vent of volcanic action, and of the originating force to which earthquake impulse is due, and that both (through whatsoever intermediate train of action) act immediately, by the development into steam, of water finding its way below the surface, and taking full account, for the important part that sea water undoubtedly plays, in such percolation and evaporation; still as we have proof undeniable, that fresh water (that of rain and snow, &c.) finds its way thousands of feet below the surface of every portion nearly of the world's dry land, we may be prepared to receive as highly probable, that seismic activity within limited distances from active volcanic vents may be more or less influenced by the supply of rain penetrating to the heated foci beneath the surface. Whatever be the source or mode of reaction, from which the supply of heat there, may be derived, the temperature at any given point is kept down, in proportion to the volume of water evaporated and discharged as steam, at volcanic vents, solfatare, &c., or in a liquid state by hot springs; the enormous absorption of heat becoming latent in the steam, being, in fact, the grand cooling agent. Under given