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POPULAR SCIENCE REVIEW. 
THE STUDY OF CHEMICAL GEOLOGY. 
By David Forbes, F.B.S., etc. 
I N the present age of rapid intellectual progress, the field of 
cultivation pertaining to any branch of scientific enquiry 
becomes each day more and more extensive in proportion to the 
advance and development of the science itself. 
Geology is no exception to this rule. The student who now- 
a-days intends to pursue this science with any chance of success, 
must not merely confine his labours to observation in the field, 
but must necessarily impose upon himself the task of acquiring at 
the same time, a sound fundamental knowledge of the principles 
of several of the collateral sciences, in order that he may thereby 
be enabled to understand and estimate correctly, the true value 
of the evidence he may collect in his travels. 
It was doubtless very different in the infancy of geology, when 
the name geologist ” was applied to the observer, who, without 
any pretension to preliminary scientific knowledge, but endowed 
with a reasonable amount of common sense and a sturdy pair of 
legs, walked over the district in all directions with a map and 
section in his hand, upon which he coloured or noted down the 
relative extent, direction, and inclination of the various rocks 
which he encountered. 
From its very nature, such work is, in great part, merely 
mechanical in character ; and as it is well known that the best 
maps, whether geographical or geological, are not always the 
production of those most eminent in the higher branches of 
these sciences, it is not improbable that the intellectual powers 
required for the execution of such duties have occasionally been 
somewhat overrated. 
In truth, the very existence of geology itself is dependant 
upon the co-operation of the allied sciences. Zoology came first 
to the assistance of the mere stratagrapher, and opened up a 
new and vast field of enquiry by insisting upon the value of 
palaeontological evidence, and showing how sedimentary deposits, 
in even the most distant parts of the earth, might be co-related 
in geological chronology, a result which could never have been 
