110 
JOUHNAL OF THE PLYMOUTH INSTITUTION. 
bodies transported, and by the character and quantity of the 
materials of the associated deposits.* These facts seem to indicate 
the existence of a more definite agency than the casual entrapments 
of open fissures • a more powerful one than the downpour of even a 
tropical thunderstorm. 
While quite admitting the possibility of some animals having 
dropped into ancient pitfalls, and the equal possibility that some of 
the cavities may have been the occasional resort of beasts of prey, 
the evidence then seems to be conclusive that the great bulk of the 
deposits must have had the fluviatile origin suggested ; and that we 
have in them the local equivalent of the ancient river gravels which 
have elsewhere been found so rich in the relics of the mammoth 
and its associates, preserved in the cavities of the limestone from the 
denuding influences which have removed it elsewhere. To dis- 
tinguish the cavern deposits from the fissure — using these terms in 
their most distinctive sense, seems to involve the conclusion that 
in the same locality two similar results were produced simultaneously 
by two wholly different sets of causes. 
The materials at command are not adequate to the tabulation of 
the various "finds" in chronological order of origin. Assuming 
the correctness of the fluviatile hypothesis, they may still be spread 
over a considerable period ; and if any of the caves were " dens," 
the time -range must have been long enough to have placed the 
cavities so occupied above the general reach of the waters, while 
the character of the fauna remained practically unchanged. Nay, 
it is quite possible that when the deposits originated, some of the 
caverns into which portions have since found their way had no 
adequate surface communication. 
As to the general date of the period to which these remains 
belong. It was certainly sufficiently remote to allow of the produc- 
tion of a present change of some 100 feet in the relative local 
positions of land and water, and beyond that of a pause of suffi- 
cient duration for the formation of the raised beach, with the time 
occupied in the continued elevation and subsequent depression of 
the submerged forest, t I cannot express the interval in any more 
* If it is safe to argue out the main question from the recorded phenomena 
of 1822 and 1 878, when the ossiferous deposits were found in the southern ends 
of the cavities, the inference would he that the current came from the north- 
ward, i.e. more in the line of the Tamar than the Plym. 
f Vide Geology of Plymouth, "Plym. Inst. Trans.," vol. v. p. 4G8. 
