56 REPORT—1850. 
and various solids in the form of fine dust or sand; but bodies in that pecu- 
liar intermediate state between mechanical suspension as sand, and chemical 
diffusion as vapour, such as constitutes common carbonaceous smoke, and 
’ whose peculiar characteristic it is to deposit a portion of its mass as a soot 
or sublimate of some sort, and the remainder to float for days or weeks 
permanently in the air in an uncondensed and unprecipitable state, do not 
seem ever to issue from the interior of true volcanic vents; so that there is 
ἃ priori the strongest improbability of smoke having ever been really seen 
to issue from an earthquake fissure. 
Compare the younger Pliny’s account of the eruption in which his uncle 
perished, where his graphic account of the thick darkness that in a moment 
overwhelmed them in absolute obscurity and almost choked them, cannot 
be mistaken for smoke, though he calls it “a thick cloud.” 
6th. Water often spouts from fissures, wells and springs, or 
bursts up in unexpected spots from the ground at the mo- 
ment of the shock; and it also is rolled out of the mouth of 
great fissures or crevasses, often in a turbid and discoloured 
state, and sometimes for a considerable time after the earth- 
quake. 
These phenomena, various and singular as they are, and apparently per- 
plexing, as we find them recorded in earthquake narratives, all arrange 
themselves into order and become of simple solution when once we have got 
the key to the whole, which is this :—They are all cases of reaction, in which 
the inertia of masses of water lodged in the earth is brought into play by the 
passage of the shock, through its solid parts, or they are secondary effects of 
those cases of slippage and subsidence, which, as we have already shown, are 
themselves secondary effects of the shock. 
This will be most rapidly made clear by a few instances. 
In the Jamaica earthquakes of 1687 and 1692, Sir Hans Sloane informs 
us, that “of all wells, from one fathom in depth to six or seven, the water 
flew out at the top with a vehement motiun,” ὃ. 6. at the moment of the shock, 
which was here a vertical one. The sudden motion of the transmitted wave 
(the earth-wave) is, to use Humboldt’s words (‘Cosmos’), “increased at the 
surface in conformity with the general laws of mechanics, according to which, 
when motion is communicated in elastic bodies, the outermost free-lying stra- 
tum tends to detach itself from the others ;” like the last of a train of billiard 
balls, which alone flies off, when the first is struck ; or to illustrate the fact 
(not this principle), if one hold a cylindrical tumbler (the well) nearly full of 
water, and suddenly raise it up a couple of feet vertically and there suddenly 
arrest it, the water will in great part leap out of the glass. 
The water of springs and natural wells is contained in the earth chiefly in 
two forms; it either lies in plates or bands of fluid in the crevices of rock 
formations, which are mostly either vertical or inclined to the horizon, and 
are usually of great length and depth and of constricted width, or the water 
lies in beds of sand and gravel, lying stretched out over large spaces, fol- 
lowiag sometimes the contour of the surface, and at others cropping out here 
and there, where the springs themselves bubble out to the surface; or 
again they lie in the vacuities which have been washed out between the 
beds of stratified rocks; or lastly, in the caverns and sinuous apertures that 
have been dissolved out of calcareous rocks, as about Trieste and in 
Ireland, &c. 
Now, in the first case, when the earth-wave passes nearly horizontally 
a 
