101 
- VLT kS t0 27 mcheS there is a diminuti on of weight on the same area 
- 37,648,938,386 tons ; being about 427,231 tons to the square mile 
Hence it may well be the case that, when the subterranean forces have 
acquired such strength as. nearly to rupture the confining strata, any con- 
siderable diminution in the pressure of the atmosphere may bring on the 
cnsis of actual disengagement." As regards the rate of the descent of rain 
at the Deluge, I have nothing to add to Professor Challis’ statements but 
may mention a remarkable fact in regard to the possible rate of its descent 
even m our own day, which was referred to at a recent (1875) meeting of 
the Geological Society by Professor Duncan, who stated that “ on °the 
Khasia hills there is a rainfall of about 600 inches annually ; and this 
tailing upon ground which does not readily absorb moisture, has cleared 
away all surface deposits, and even excavated coombs in the granite.” 
THE REV. PROFESSOR CHALLIS’ REPLY. 
Professsor Challis, who was not present at the meeting, having received 
a copy of the printed account of the discussion of his paper, requested that 
the following reply to some ot the remarks made by the speakers might be 
added to the discussion : — 
Mr. Henslow appears to have misunderstood the view I take of the 
physical operations by which the Deluge was produced. It is true that I 
consider the primary disturbing cause to have been an abnormal increment 
of the temperature of the interior of the earth ; but the accession of heat is 
not supposed to “ cause upheaval of the sea-bottom,” nor to have any other 
immediate effect than that of generating excessive evaporation at the surface 
of the sea, in consequence of which there would be a downfall of “ torrents 
of rain” on the land. For reasons which I adduced, it is not improbable 
that the amount of water which by this means would be transferred from 
sea to land might have the effect of disturbing the equilibrium of the earth’s 
crust, which, adopting Sir John Herschel’s view, I suppose to be resting on 
a molten sea. Hence, vertical oscillations of the crust, accompanied by 
transverse movements and occasional ruptures, might be the result, producing 
eventually the configuration of islands and continents, and the superficial 
irregularities, which we witness at the present day. I make no objection to 
the speculations mentioned by Mr. Henslow, according to which results 
like these might have followed from a change of the inclination of the earth’s 
axis, and the consequent mechanical action of “ an enormous accumulation 
of ice at the poles.” But failing to see how such views could conduct to an 
explanation of the particular phenomena of the Noachian Deluge, as described 
in Scripture, and having found that these phenomena might be intelligibly 
accounted for by the supposition of an abnormal increment of terrestrial 
temperature, I had no alternative, considering the purpose of the paper, but 
