Vol. 58.] ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixv 
Black Sea and its inlets. In the same category we must place 
the paper ‘On the Origin of certain Concretions in the Lower Coal- 
Measures’ recently communicated to this Society by Mr. Stocks. 
At the beginning of the century but little was known as to the 
composition of the sedimentary rocks. The methods available for 
their examination were of a very primitive character, and wholly 
insufficient in many cases to supply the necessary data for ascer- 
taining their mode of formation. The discovery and application of 
precise methods of chemical analysis, and the introduction of the 
microscope, have placed us in an entirely different position trom 
that occupied by our ancestors. Just as Bischof’s name stands out 
pre-eminently in the domain of chemical geology, so does that of 
Ehrenberg in the field of microscopic petrology as applied to sedi- 
mentary rocks. The proof which he supplied of the important 
part played by minute organisms in building up siliceous and 
caleareous deposits enormously enlarged our conceptions of the 
duration of gevlogical time, and threw a flood of light on the con- 
ditions under which certain groups of stratified rocks have been 
formed. The work which he inaugurated was carried still farther 
by the introduction of the study of thin slices, and has been 
continued with uninterrupted success up to the present time. It is 
too well known to need more than a passing reference. 
Much chemical and petrographical work has been done on sedi- 
mentary rocks: at the same time it is very small, in comparison with 
what remains to be done. Petrologists have been content for the 
most part to leave these rocks to the paleontologists, who have 
searched them for fossils with the greatest zeal, but who, in most 
cases, have had neither the time nor the inclination to pay attention 
to the structure and composition of the deposits. This is a mis- 
fortune, for itis only by a combination of petrographical, paleonto- 
logical, and stratigraphical work that the natural history of the 
sedimentary rocks can be made out. In reading papers of the 
greatest stratigraphical importance, in which the distribution of 
fossils is described, and in studying the rocks in the field, I have 
often been much struck with the extreme meagreness of the pub- 
lished information as to the nature of the deposits and the mode 
of occurrence of the fossils. It 1s, perhaps, too much to expect one 
man to study these rocks from all points of view; and if so, 
the remedy must be found in co-operation, which is certainly 
becoming more and more necessary as the complexity of the problems 
increases. It must not, however, be forgotten that there are some 
