496 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



very earliest stages of its history it was more or less bound 

 up with mineralogy, which stands related to chemistry 

 as palaeontology to biology, and with this inorganic 

 chemistry it has developed side by side. But it has added 

 to mineralogy the great snb-science known as petrology or 

 petrography, which deals with all the mineral constituents 

 of the earth-crust and with their groupings and inter- 

 relationships, actual or theoretical, present and past. 

 Indeed, within the last ten years or so, to not a few who 

 call themselves geologists, petrography is the be-all and 

 end-all of the science itself. Fortified by the advantages 

 afforded by the invention of the microscope and its great 

 improvement in recent years, as well as the advance in 

 chemistry and optics, some of us are tempted to pay too 

 much attention to the study of rocks and rock slides, to 

 the neglect of other branches of the science. There is 

 no likelihood that this side of geology can be ignored. It 

 has opened out to us the grandest views of the origin and 

 evolution of rocks in general. The day is fast approach- 

 ing when, taught by Nature's methods, the student of this 

 branch of geology may learn to imitate and manufacture 

 in their laboratories even the natural jewels which are 

 the most valuable of all the mineral products known to 

 mankind. 



The second stage in the history of our science after its 

 mineralogical childhood was its glorious youth, when in 

 company with its biological sister it entered irpon the 

 study of fossils and of the geological formations. And 

 with what a wealth of natural facts and natural phenomena 

 has this branch of our science enriched human knowledge 

 and human philosophy. It has unravelled the structure 

 of almost all of the rock formations of the British Islands 

 and made them the accepted model for the whole scientific 

 world. It has proved that in these formations we have 



