162 
A cordial vote of thanks was offered to Mr. Harrer for his 
valuable and instructive gift. 
Dr. Wrieut having concluded his paper on the Ammonites, 
which is included in the foregoing report, the Rev. Dr. SuyrHz 
proceeded to give an exposition of Microscopy as applied to the 
discrimination of Igneous rocks. 
As the time was restricted, the author, instead of reading 
his paper, made a running comment on the general subject, 
his object being to enlist the attention of Geologists in a study 
which, strange to say, took its origin—as regards the newer 
methods of examination—in this country, yet had languished 
here, whilst in the United States of America and on the 
continent of Europe it had gone ahead of us, and we bad to go 
to foreigners to learn. Not to speak of the continental workers, 
who could boast of quite a bibliography of results, he could point 
to Ferpinanp ZrrKew’s fine work on the Igneous Rocks of the 
Western Territories of North America, published in 1876 at 
Washington, by the Engineer Department of the United 
States army. This book contains a digested account of the 
examination of 2500 thin sections of rocks scrutinized under 
the microscope. He also mentioned that the Geological Record 
for 1877 gave a list of 150 works upon Petrology published in 
Europe and America in the course of a single year. In England 
one elementary text-book had been published on the study of 
rocks—Rutley’s Petrology, 1879—it was already bought up, and 
the author going to press with a new edition. 
The old method of study of the Igneous rocks was confined 
to chemical analyses of constituent minerals, or to the dry 
method with the blow-pipe, and to crystallography ; but how a 
rock was built up, or how a crystal was formed, observers could 
not tell us; in fact they held the erroneous notion that crystals 
were homogeneous, whereas the case is quite the contrary. 
The method of examining the Igneous rocks at present is 
microscopical. For this we begin by reducing a given portion 
of the rock to be examined under the microscope into thin 
sections, as thin as the fine inner skin of an onion, in some 
cases, so as to be capable of transmitting light, and then 
