368 John Young—Structure of Shell of Chonetes. 
encumbers it with his great ice-sheet, which pervades his pages like 
a nightmare. He has no hesitation in assigning the tumultuous accu- 
mulations of shingle and boulders of Central England as proving the 
presence there of excessive floods and torrents. ‘‘ Buckland, Cony- 
beare, Sedgwick, Phillips, and the early observers,” he says, ‘‘ were 
much struck with the great quantities of shingle and the numerous 
erratics that strew the midland districts, and which occur even farther 
south, as in Cornwall and Devon, and they probably came very near 
the explanation of the facts when they attributed the transport of the 
materials to the action of great debacles” (Ice Age, p. 364). | 
All this is most probable. The point where we separate from Mr. 
Geikie is when he assigns a cause for these debacles and makes 
them local instead of continental. He is too experienced to explain 
the distribution of the gravel directly by his ice-sheet, but he connects 
it with the ice in another way by postulating that great and rapid 
floods were caused by the sudden melting of the ice-cap. In regard 
to this notion, I must be allowed to quote a very pertinent and 
sound argument of Mr. Smith, of Jordan Hill (Journ. Geol. Soc. 
vol. ii. p. 36). He says, “The melting of ice could never pro- 
duce a debacle, in the rigid sense of the word. I mean such a 
debacle as would be produced by the bursting of a waterspout, or 
the head of a reservoir, or an earthquake-wave: the laws of matter 
prevent it. The conversion of sensible into latent heat is necessarily 
a work of time. Floods, possibly of great violence, might result 
from such a cause, capable of moving the greatest masses, but their 
action would be continuous, and they would necessarily separate the 
larger from the smaller fragments, and all of them from the clay in 
which they are imbedded. They would be arranged both according 
to their size and their gravity; but neither of these is the case, and 
I must conclude, with Sir James Hall, that such effects are ‘ inex- 
plicable by any diurnal cause.’ Again, as the same author says, 
floods caused by this means must run down-hill. If ice can move 
up mountains, which I, for one, beg to contest, until some proof is 
available, it is clear that water cannot, and therefore, water merely 
drawing from a rapidly-thawing ice-sheet could not distribute gravels 
over hill and dale irrespective of the drainage of the country, and 
which in many cases has evidently travelled up-hill.” Mr. Smith, in 
view of these difficulties, postulates, as the only available cause, a 
rush of water such as is caused by earthquake-waves, and I do not see 
how he is to be gainsaid. 
(To be continued.) 
V.—On tHe Suett-Strrucrure or Caovzrzes Lacunsstav4, Dr Kon. 
By Joun Yona, F.G.S., 
Of the Hunterian Museum in the University of Glasgow. 
A hye specimens selected for illustration of the shell-structure of this 
species of Chonetes were found in a bed of shale in the Lower 
Carboniferous Limestone series at Capelrig old quarry, in the parish 
