128 THE PROGRESS OF SCIENCE n 



the operations of Nature have taken place in the 

 youngest geological epochs. 



An incalculable benefit has accrued to geo- 

 logical science from the accurate and detailed 

 surveys, which have now been executed by skilled 

 geologists employed by the Governments of all 

 parts of the civilised world. In geology, the 

 study of large maps is as important as it is said to 

 be in politics; and sections, on a true scale, are 

 even more important, in so far as they are essen- 

 tial to the apprehension of the extraordinary 

 insignificance of geological perturbations in rela- 

 tion to the whole mass of our planet. It should 

 never be forgotten that what we call "catas- 

 trophes," are, in relation to the earth, changes, 

 the equivalents of which would be well represent- 

 ed by the development of a few pimples, or the 

 scratch of a pin, on a man's head. Vast regions of 

 the earth's surface remain geologically unknown ; 

 but the area already fairly explored is many times 

 greater than it was in 1837 ; and, in many parts 

 of Europe and the United States, the structure of 

 the superficial crust of the earth has been inves- 

 ti^ated with great minuteness. 



The parallel between Biology and Geology, which 

 I have drawn, is further illustrated by the modern 

 growth of that branch of the science known as 

 Petrology, which answers to Histology, and has 

 made the microscope as essential an instrument 

 to the geological as to the biological investigator. 



