y> OU'II.IM B 01 1 II I.D-C.KOLOCY 



map or note-book, the different rock-masses which may 

 occur in I colours arc of course ulti- 



mately employed for representing the geological forma- 

 tions on the finished map. lint a few bits of coloured 

 pencils carried in his pocket save the geologist much 

 needless writing in the field. To a red, blue, green, or 

 yellow dot or line he attaches a particular meaning, and 

 he places it on his map without further explanation than 

 the local peculiarities of the place may require. 



Such are the few prime instruments required in fi Id 

 geology. We may add others from time to time, accord- 

 ing to the nature of the work, which in each region will 

 naturally suggest the changes or additions that may be 

 most advantageously made. A small protected bottle 

 of weak hydrochloric acid, or some powdered citric acid, 

 is sometimes of use in testing for carbonates, particularly 

 in regions where rocks of different characters come to 

 resemble each other on their weathered surfaces. When 

 Sir William I>ogan was carrying on the survey of the 

 I^aurentian limestones of Canada, he received much 

 help from what he called his "limestone spear." This 

 was a sharp-pointed bit of iron fixed to the end of a pole 

 or a walking-stick. He enlisted farmers and others in 

 his operations, instructed them in the use of the spear, 

 and obtained information which gave him a good 

 general notion of the distribution of the limestone. The 

 spear was thrust down through the soil until it struck the 

 rock below. It was then pulled up, and the powder of 

 stone adhering to the iron point was tested with acid. 

 If, after trying a number of places all round, the observer 

 uniformly obtained a brisk effervescence when th 



