PROGRESS OF MICBOSCOPIOAL SCIENCE. 
127 
in tlie recent discussion of the ' Challenger's ' researches to leave him 
out of sight. He evidently thinks so himself, as the following extract 
from a letter in a late number of ' Nature ' will show : 
" When Prof. Wy ville Thomson published his recent volume giving 
the results of the deep-sea researches conducted by himself and his 
colleagues, Dr. Carpenter, Mr. Jeffreys, and others, he also gave a 
sketch of the history of the subject ; but he made no mention of my 
memoir on the Microscopic Organisms of the Levant Mud, published 
in 1 847 in the Transactions of the Literary and Philosophical Society 
of Manchester, though this memoir had been referred to from time to 
time by Dr. Carpenter, Messrs. Parker and Eupert Jones, and others, 
and was, next to Ehrenberg's discovery of the microscopic structure of 
chalk, the starting-point of all these deep-sea investigations. It was 
the first to call attention to the existence of foraminiferous deposits in 
the sea, and to insist upon the organic origin of all limestones except 
a few fresh-water Travertins, in opposition to the theory of chemical 
deposits that had previously been advocated in the works of Phillips 
and other geologists. Dr. Wyville Thomson in a recent article points 
out that extensive areas of the deep-sea bottom are now occupied 
by a reddish earth, and he has arrived at the conclusion that this 
earth is a residue left after all the calcareous Globigerinee and other 
such elements have been removed by the solvent action of carbonic 
acid accumulated in these deep waters. In my memoir I arrived at 
the same conclusion from the study of the marine Tertiary deposits, 
containing Diatomacese, of Bermuda, Virginia, and elsewhere. I may 
perhaps be permitted to republish the following extracts from that 
memoir, since it is not now readily accessible to all the numerous 
naturalists who are interested in this question : 
" ' In the recent deposit of the Levant we have generally an admix- 
ture of calcareous and silicious organisms. In some localities the 
latter are more sparingly distributed than in others ; in a few instances 
they are almost entirely absent. The same admixture occurs in the 
recent sands from the West Indies. The soft calcareous mud from 
the bottom of the lagoons of the Coral Islands contains a considerable 
number of similar silicious forms, and corresponding results have been 
obtained in most of the marine sediments from various parts of the 
globe, examined by M. Ehrenberg. 
" ' On the other hand, the infusorial deposits of Bermuda and 
Virginia are altogether silicious. Not one calcareous organism exists. 
The silicious forms comprehend the majority of those which I have 
described from the Levant, many of them being not only similar, 
but specifically identical, and the manner in which they are grouped 
together in these distant localities indicates something more than 
mere accident. Indeed, we want nothing but the calcareous structures 
to render these Miocene strata perfectly analogous to those now 
in process of formation, both in the Mediterranean and in the West 
Indian seas. Are these silicious deposits, so void of any calcareous 
organisms, still in the condition in which they were originally accumu- 
lated? or were they once of a mixed character, like those of the 
Levant, having been subsequently submitted to some chemical action 
VOL. XIII. L 
