GEOLOGICAL MAPS jS 



acquires a thoroughness of grasp attainable in no other 

 way. The best field-geology is of that kind which care- 

 ful and minute map making requires. It is not, of 

 course, impera: m actual survey should be made 



t.y the geologist ; but he must proceed in such a way 



his observations, if tabulated and placed u; 

 map, would m .1 good geological one. 



the kind of work required in the prepara- 

 tion of geological maps illustrates most completely the 

 nature and methods of field-geology, I shall describe the 

 construction of these maps as practised in this country. 

 The reader will bear in mind that, though he may never 

 draw a geological boundary-line, nor part in a 



geological survey, he cannot attain excellence in the 

 practical pursuit of geology in the field, without going 

 through the training whic h, if need be, would qualify 

 him for becoming a professional geologist How this 

 should be the case will, I hope, become clear in the 

 sequel 



Let us first consider what a "geological ma; 



meaning now attached t<> this term differs very 

 mm h from that with which it was associated not very 

 many years ago. In the early days of geology, those 

 who devoted themselves to this branch of science were 

 .ithcr than what we should now call geolo- 

 gists. They termed their subject "geognosy," mean- 

 ing thereby to indicate their object to be the increase 

 of their knowledge of the minerals and rocks of the 

 earth. They constructed what they called " geognostkal 

 maps," on which the positions of marked varieties of 

 minerals and rocks were shown, but without any attempt 



