702 Earthquakes and Electricity . [December, 
communication between the earth and the upper regions of 
the atmosphere ? ” — (Hist., 459.) 
The next English writer to advert to the question appears 
to have been William Nicholson, who in 1787 wrote “ An 
Introduction to Natural Philosophy.” He adduces expe- 
rience to combat the idea that earthquakes can be occasioned 
by subterranean explosions. But apparently he alludes to 
explosions of vapour , for he mentions the notion as “ the 
common opinion.” His notice is valuable as tending to 
show one of the possible reasons for the rejection, by the 
physicists of those days, of the theory of an electrical 
origin ; for doubtless the only aCtion they would conceive to 
result therefrom would be that of a subterranean explosion 
somewhat akin to a subterranean explosion between two 
clouds. Since, however (as Nicholson shows) faCts demon- 
strated that the operation of earthquakes was chiefly of a 
superficial nature, the upheaval of the ground that must 
inevitably attend an explosion from below was probably 
deemed to be by no means in accordance with observation, 
and the electrical theory was therefore discredited. But 
to physicists of the present day conversant with the important 
class of electrical discharges known as leaks the surface 
nature of the aCtion of earthquakes would appear to present 
a stamp of confirmation, rather than a stumbling-block. 
A long interval now ensues, and Humboldt’s “ Cosmos ” 
would seem to be the next important work that dealt with 
the question. The English translation (by Colonel, after- 
wards Sir Edward, Sabine, F.R.S.) of this “ Sketch of a 
Physical Description of the Universe” was published in 
1847. Besides the quotation from Pliny to which we have 
already alluded, much valuable information on the subject 
of earthquakes is furnished by Humboldt. He says : — 
“ Active volcanoes may be regarded as safety-valves for the 
country in their immediate vicinity” (i., 202). . « . “ The 
destruction of Lisbon, of Caracas, of Lima, of Cashmeer 
in 1554, and of so many towns of Calabria, Syria, and Asia 
Minor, shows that on the whole the most violent shocks do 
not usually take place in the vicinity of still aCtive volca- 
noes ” (i., 202). In allusion to the substances ejected at 
times from the earth — such as hot water, steam, noxious 
gases, mud, smoke, and flames — he says, “ Do gaseous 
fluids issue from the interior of the earth and mingle with 
the atmosphere ? Or are these meteorological processes the 
effects of a disturbance of the electricity of the atmosphere 
by the earthquake ? ” (i., 205). In regard to the association 
of earthquakes with thunderstorms he says, “ On the coasts 
