280 Reports and Proceedings. 
should make us cautious how we draw conclusions from the presence 
of a single fossilin a stratum. He stated that there were two small 
crustaceans, Viphargus fontanus and Crangonyx subterraneus, found 
in the wells of Wiltshire, Berkshire, Hampshire, and Devonshire. 
These animals were both colourless and blind, showing how dark 
had been their dwelling-place. Mr. Pycroft next entered into the 
subject of limestone-caverns, observing that they are or have been 
the natural drainage-channels of the earth’s crust, and that they 
exhibit the phenomena of underground rivers on the grandest scale. 
Among other points he particularly discussed, was the frequency and 
violence of floods in these chasms. He stated that when a traveller 
. visits one of these caves, such as the Peak Cavern, he cannot bring 
his mind to believe that all this grand vault has been excavated by 
so insignificant a small stream as that now running through it. But 
we must remember that it is with these natural drainage-channels 
as it is with the London sewers: one leads into another; and in the 
season of winter-storms, the ‘main’ in one case and the cavern in 
the other is not more than large enough to carry off the torrent. In 
the case of the limestone-caverns, the torrent is furious indeed, from 
the varying size of the channel, the cascades, the generally inclined 
form of the floor, and the frequent turns. He discussed at some 
length the bearing which the study of these phenomena had upon 
the unravelling of the mystery of bone-caverns, and said that bones 
washed or fallen into a fissure in a limestone-country might in 
process of time be discovered in caverns many miles distant. Mr. 
Pycroft next described the animals inhabiting these dark rivers—the 
blind and almost colourless Proteus, and the blind Crustacea and 
Fishes of the Adelsberg, with blind Spiders, Beetles, Crickets, 
and Rats. He next entered into the subject of the enormous 
caverns, hundreds of miles in extent, known to exist in the neigh- 
bourhood of voleanos — of their having communication by open 
channels with the waters of the ocean, and with those of fresh- 
water lakes and rivers. ‘The ashes which overwhelmed Pompeii 
were proved by the microscope to be in great part composed of the 
siliceous diatoms which once lived in the neighbouring streams ; 
and Humboldt states that he has seen the little fish Pimelodus 
Cyclopum thrown from apertures on the sides of the mountains of 
Quito living, though ejected with scalding water. 
Having shown that the rain, the rivers, and the seas all have 
communication with the interior of the earth, he next proceeded to 
discuss the use to which this free supply is put in the economy of 
nature. He showed that in crystallization, in chemical decompo- 
sition, and in all the chemical processes the earth’s crust undergoes, 
water is absolutely necsseary ; that it is the bond of union between 
geological formations, without which each would be isolated and un- 
connected with all others not in immediate contact; that water will 
penetrate to any depth, even until it reaches a level, the temperature 
of which is so high that the expansive power of the heat counter- 
balances the gravitating power of the water; that there is at this 
level a zone in the crust of the earth, probably not of a very high 
