OH. xxxi. SUMMARY. 291 



his time it could be studied accurately and usefully by all 

 who cared to take time and trouble. 



Thus, even without mentioning the science of medicine, 

 which had grown far beyond our power of following it up ; or 

 the wonderful work with the microscope, which had increased 

 rapidly since the days of Grew and Malpighi, biology grew 

 during the eighteenth century into a group of sciences, the 

 works upon which would fill a library, and each branch of 

 which requires the study of a lifetime to master it. 



Geology Side by side with biology arose, about this 

 time, the modest and almost unnoticed science of the earth, 

 then generally called physical geography, but now known as 

 Geology. This was a small seed sown in the eighteenth 

 century, to grow into a large tree only in our time ; yet it 

 was a great step when Scilla insisted that fossils were the 

 remains of living beings, and that the rocks containing them 

 were formed gradually under lakes or seas. And when 

 Werner taught men to study the earth's crust, and Hutton 

 forced them to see that Nature is, and has always been, 

 building up our present world out of the ruins of the past, 

 the foundations were laid for the real study of the earth and 

 its formation. Meanwhile William Smith toiled over 

 England, mapping out the position of each rock as he saw 

 it, and thus he led the way to a long series of careful 

 observations, by which the whole geology of England has 

 been worked out. 



Chemistry. But the science which before all stands 

 forth in the eighteenth century is chemistry ; for here the 

 discovery of the different gases led to certainty where all had 

 been guess-work before, showing the actual chemical changes 

 which are taking place on all sides in the world around us, 

 and teaching men to weigh and test invisible substances, and 

 not to rest satisfied with their knowledge of any substance 



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