2i66 D. Forbes — On the Study of Chemical Geology, 



II. — Mr, David Forbes on the Study of Chemical Geology. 



THE Popular Science Eeview for July contains, among other 

 interesting matter, an excellent article, by Mr. David Forbes, 

 F.K.S., on the Study of Chemical Geology. 



The student, writes Mr. Forbes, who now-a-days intends to pursue 

 the science of Geology 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 geo- 

 graphical or geological, are not always the production of those most 

 eminent in the higher branches of the 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 dependent upon 

 the co-operation of the allied sciences. Zoology came first to the 

 assistance of the mere stratigrapher, and opened up a new and vast 

 field of enquiry by insisting upon the value of palseontological evi- 

 dence, and showing how sedimentary deposits, in even the most dis- 

 tant parts of the earth, might be co-related in geological chronology, 

 a result which could never have been arrived at by the mere exami- 

 nation of their mineral character and position in the field ; mathematics 

 and astronomy lent their aid in, solving many important problems 

 connected with the phenomena of our sphere ; and mineralogy was 

 required to determine the mineral components of which its crust 

 was formed ; whilst a knowledge of optics and the use of the micro- 

 scope enables the geologist to extend his investigations far beyond 

 the limits to which his naked eye could otherwise convey him.^ 



When, however, the geologist advances further, and desires to 

 study something more than the mere external forms and physical 

 characters of the materials of which our globe is built up, he is com- 

 pelled to call in the aid of chemistry, for it is by chemical science 

 alone that he can be enabled to demonstrate the true nature of these 

 materials, to explain their formation or origin, or to discover the 

 causes which have produced the changes or alterations which they 

 have already experienced, or which they may now be undergoing. 



^ Vide " The Microscope in Geology," Popular Science Review, vol. vi., Oct. 1867, 

 p. 355, etseq. 



