114 Transactions of the Royal Microscopical Society. 
eratified with the fact that so many of these papers were devoted 
to important general questions, and were not confined to individual 
observations, having no apparent bearing on any of our great 
scientific theories. After the reading of these papers I in most 
cases endeavoured to express my own opinion on the various sub- 
jects, and I therefore think it less desirable to again pass them in 
review, than to direct your attention to a special branch of research 
with which I have been occupied during the last half year. 
The Application of the Microscope to Geology. 
Our late distinguished Honorary Fellow, Ehrenberg, was the 
first to apply the microscope to any considerable extent to the 
study of geological questions. He, however, directed his attention 
mainly to the organic constituents of rocks. The general structure 
of hard stony masses has lately been much studied both in England 
and on the Continent, especially that of various igneous rocks, or of 
highly altered strata which more or less closely resemble some 
of them. So far as I am aware, very little has been done in the 
application of the microscope to the investigation of the nature and 
origin of loose and unconsolidated sands and clays. I was led to 
study these in full detail, because it appeared to me desirable to 
thoroughly understand the characters of the raw material before 
attempting to speculate too freely on the nature, extent, and 
cause of the changes which have subsequently occurred during 
consolidation or metamorphism. I was also led to examine cer- 
tain questions more fully on account of having undertaken to 
investigate and describe the mineral constituents of the deep ocean 
deposits brought back by the ‘ Challenger.’ 
Seeing, then, that this great subject had hitherto been so much 
neglected, and is yet the very foundation of our knowledge of the 
history of those rocks, which constitute a large part of the acces- 
sible framework of our globe, it appeared to me desirable in my 
address this evening to attempt to treat this subject in a systematic 
manner, combining together some well-known facts with others 
that have perhaps attracted little or no attention, in order to make 
the whole more continuous and complete. Time will not, however, 
allow of my entering into full detail, and will compel me to confine 
my remarks to one principal question. 
Structure of Stratified Rocks. 
The study of the microscopical structure of stratified rocks is 
very naturally divisible into two very distinct questions, viz. the 
nature and origin of the materials which were deposited, and 
the changes which have occurred since deposition; but on the 
present occasion I must confine myself almost entirely to the former 
of these two divisions. 
