54 
Wallich_, on Siliceous Organisms. 
Saipse again^ in inconceivably vast numbers_, afibrd almost the 
entire food of the largest orders of cetaceans; and I there- 
fore think we are able to infer^ with certainty^ that, in the 
complex stomachs and intestines of the latter, the further 
process of aggregation of siliceous particles goes on upon a 
gigantic scale, aided by the presence of the alkalies, and that 
the aggregated masses being voided at intervals, slowly sub- 
side, without disruption, to the bed of the ocean. 
It must also be borne in mind that the whales are gre- 
garious animals, frequenting particular latitudes at particular 
seasons, and migrating under certain circumstances ; and that 
to the operation of these causes the irregular character of any 
exuvial deposits might naturally be referred. And lastly, 
that it is by no means essential that chemical forces should 
operate upon the siliceous aggregations, whilst yet within the 
intestinal canal of the cetaceans, to such an extent as to 
render their concretion at all complete. But there can be 
no difficulty in conceiving that during the passage of such 
aggregations through their cavities a sufficient degree of 
chemical action might take place to ensure their continuance 
in the aggregated state until they reach the pulpy cretaceous 
stratum destined to be their final resting-place ; whilst amidst 
the undisturbed quietude of those depths each fragment of 
the numberless forms of organic life, with which the seas of 
the secondary epoch teemed, would naturally become a 
nucleus, around which the still plastic siliceous material 
might slowly gather and consolidate. 
The coprolites, derived from another series of oceanic 
monsters that frequented the seas of the same epoch, furnish 
us with an analogy, in so far as the deposition of animal 
exuviae in masses and at great depths is concerned. But in 
this case the nature of the exuvise left little to be done, 
either by chemical or mechanical action, after their extrusion. 
None of the theories hitherto ofi'ered have indicated, in a 
satisfactory manner, any means whereby the siliceous ele- 
ments could reach the sea-bed in already aggregated masses. 
It is essential, I conceive, that a certain amount of aggrega- 
tion should take place in those masses before arrival at this 
stage of their history. For, as already stated, had the 
cohesive tendency of the siliceous particles alone determined 
the character of their formation, the nodular concretions 
must of necessity have been found arranged in obedience to 
some definite law, both as regards distribution and structure. 
The theory now offered is by no means intended to super- 
sede others, but only to be auxiliary to them, by pointing out 
an agency through which the widely scattered siliceous parti- 
A 
