xv SECTION -DRAWING >M 



where every itnturn is exposed lo view. Evidently a 

 section of this kind requires good exposures of rock and 



The horizontal section, on the other hind, roust often 

 be constructed where exposures of rock are few, where 

 minute ff^ft^T^f**^* 1 ** are I in possible, and where the 

 highest skill of the field-geologist is taxed to unravel the 

 meaning of the (acts he notes upon the surface, and to 

 show their bearing upon the relations of the rocks below 

 ground The first point I would remark in the drawing 

 of horizontal sections is, that if not at the beginning, at 

 least in some pan of his experience, he will find the great 

 advantages of plotting them on a true scale, that is, with 

 the height and length on the same scale, and thus training 

 his eye to the true proportions of the different parts of 

 the topography. Of course this is often impossible, for 

 the ground may be low, and to show its true form in a 

 section might require an extravagant and unnecessary 

 length of paper. St ill t he geologist who would preserve, as 

 he should, the relations between the external form of the 

 ground and the structure of the rocks below it, will always 

 endeavour to exaggerate the height of his sections as little 

 as possible. I believe that nothing has tended so much 

 to perpetuate erroneous notions regarding the physio- 

 graphy of the land as such distorted sections, sometimes 

 almost grotesque in their exaggeration of natural forms. 



As an example of the disregard which some able 

 observers have had for truth of outline in their sections, 

 there are inserted on the following page two sections of 

 the same hill. On one of these (AX an eminent miner- 

 alogist, seems to have been content to represent in a kind 



