MAPPING. 17 



all. (See some excellent remarks on, and illustrations 

 of, this subject in Sir Charles Lyell's " Students' Ele- 

 ments of Geology," p. 60 [1871].) 



The above are general ideas which it will be well to 

 have impressed on the mind, as in tracing a boundary 

 their principle will yield immense assistance. Of course 

 in practice the ground must be gone over, and the actual 

 line followed, for dip may change anywhere, and it often 

 does so in places where it is least expected. Faults also 

 may occur, and these interrupt suddenly the continuity 

 of a line, and involve a fresh one of their own. 



i) M J* K A H 



CHAPTER II. .! 

 MAPPING (continued). C A 1 ^ j {< \ ) ] > \ T f 



Examples of Tracing Boundaries Mem 



Symbols Drift Deposits. 



Examples of Tracing Boundaries. Having then pro- 

 cured a map of the district to be surveyed, cut it into 

 two slips to fit the map-case, and provided ourselves with 

 compass, scale, hammer, and so 'on, we will proceed to the 

 actual work before us. The slip represented by fig. 5 

 (but of course without the geological lines thereon) is to 

 "be the scene of our operations, and we start, in imagina- 

 tion, from the church, which, we are inclined to think 

 from the white appearance of the soil hereabouts, stands 

 on the Chalk formation. By an examination of the 

 pond on the other side of the road this supposition is con- 

 firmed, for the excavation has been made three or four feet 

 deep, and its sides here and there exhibit sections of that 

 well-known rock. We note this fact by a symbol of 



