Xliv PROCEEDINGS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
Photographic Members will support the efforts of the Photographic 
Committee a little more heartily than they have done in the past* 
both in the way of attending the meetings and of adding to the 
interest of these meetings by contributing short papers or notes or by 
exhibiting examples of their work. It should always be remembered 
that even indifferent work is as instructive, for purposes of com¬ 
parison, as work of a higher standard. 
I should at the same time like to draw the attention of all 
interested in geology to the course of six lectures on Historical 
Geology and Palaeontology, to be delivered in February next, by 
Mr. James B. Corr of Dundee. This will be a rather more systematic 
course than the one which he delivered to us last spring, which was 
mainly introductory. Geology is such a very wide subject that even 
the student who has already made considerable progress in it must 
benefit by having his memory refreshed by such a course as this, and 
I trust, therefore, that the attendance will be at least as large as last 
time. As certain expenses are incurred in connection with these 
lectures, a charge of five shillings is made for the course. 
The last item of the Society’s work to which I wish to refer is 
the Children’s Essay Competition, and this I do merely to remind 
the young people that their essays should be sent to the Secretary 
or the Curator before the close of the year. The subject for this 
session, namely, “The Divisions of the Animal Kingdom as illus¬ 
trated in the Index Museum,” has been chosen with a view to induce 
the children to take a more systematic interest in the world of 
animal life around them. The subject for last year was purposely 
an introductory one, in order to ascertain how far the children could 
grasp the general scope and aim of the Museum as an introduction 
to the study of natural history. I need hardly repeat that the greater 
the number of children taking part in the competition the better I 
shall be pleased. 
In regard to the Museum itself, the department which has 
engaged most of the attention both of the Curator and myself during 
the past summer is 
THE ROCK COLLECTION IN THE INDEX MUSEUM. 
The science of Geology, as I have already indicated, is a very 
wide one. It embraces the history of the evolution of the earth’s 
crust, and therefore deals with the materials of which that crust is 
composed from many points of view. One department, for example, 
has to do with the historical sequence in which these materials have 
been built up, another takes note of the vestiges of life which are 
scattered through them, and so on. The department which the 
collection under consideration is intended to illustrate takes cogni¬ 
sance of rocks as definite and differentiated structures, without 
reference to their position in the geological record, or the lessons 
which they teach regarding the action of the various forces which 
have moulded the earth’s crust. This department of Geology is 
known as Petrology, or the study of rocks as such, pure and simple. 
It may be said to correspond to anatomy in the domain of organic 
