72 
small portion of the earth’s mass. For it would seem im- 
possible to explain the remarkable fact that, after taking 
account of the above-mentioned elevations and depressions, 
the mean form of the superficies of the solid parts coincides 
with the form of the ocean-surface, unless that mean form 
were determined by the conditions of the equilibrium of a 
liquid mass constituting nearly the whole of the interior. 
Adopting, for the above reasons, the hypothesis of a liquid 
interior of the earth, I propose, in the next place, to discuss 
briefly, with the view of applying the results of this discussion 
in the subsequent argument respecting the Deluge, the pheno- 
mena and probable causes of volcanoes and earthquakes. In 
treating of this subject I cannot do better than refer to what 
is said about it by Sir John Herschel in an excellent work en- 
titled Familiar Lectures on Scientific Subjects. (Strahan, 1867.) 
The first lecture is on “ Volcanoes and Earthquakes,” the pheno- 
mena of which it gives a very intelligible account of in familiar 
terms, together with a theory of their causes, which, I believe, 
in all essential points is due to Herschel himself. It will con- 
tribute much towards elucidating my subject to quote some 
passages from this lecture, which I shall do by citing the 
numbers within brackets, placed for reference at the beginnings 
of the paragraphs. 
In paragraph (3), speaking of the geological changes “ we see 
going on,” the author says, “We see everywhere, and along 
every coast-line, the sea warring against the land, and overcom- 
ing it; wearing and eating it down, and battering it to pieces ; 
grinding those pieces to powder; carrying that powder away, 
and spreading it out over its own bottom, by the continued effect 
of the tides and currents.” Looking at our chalk-cliff’s, “ what 
do we see? Precipices cut down to the sea-beach, constantly 
hammered by the waves and constantly crumbling : the beach 
itself made of the flints outstanding after the softer chalk has 
been ground down and washed away; themselves grinding one 
another under the same ceaseless discipline ; first rounded into 
pebbles, then worn into sand, and then carried out farther and 
farther down the slope, to be replaced by fresh ones from the 
same source.” 
“ The same thing is going on everywhere, round every coast.” 
“ And what the sea is doing, the rivers are helping it to do. 
Look at the sand-banks at the mouth of the Thames. What 
are they but the materials of our island carried out to sea by 
the stream ? The Ganges carries away from the soil of India, 
and delivers into the sea, twice as much solid substance weekly 
as is contained in the great pyramid of Egypt. The Irawaddy 
