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THE BOOK OF NATURE STUDY 



work, and to demonstrate the value of contouring in bringing 

 out the exact shape of features from different points of view 

 (Fig. 46). It will become clear that, excellent as is the method, 

 it is only really exact on the contour lines themselves and tells 

 nothing of the ground between, except that it is of a height 

 somewhat intermediate between that of the contours. It is here 

 that hachuring comes in to furnish supplementary aid as to the 

 profile of slope between contours, whether convex, concave, or 

 straight. 



The first sections would naturally be drawn along straight 

 lines, but later they can be taken along roads, streams, railways, 

 etc. They should also be drawn on varying scales, starting naturally 



FIG. 46. Sections along the line C, D, Fig. 44. The lower one is to 

 natural scale, the upper has the heights exaggerated five times. 

 Construction lines are ruled in the upper figure. 



from the actual scale of the map. The study of several sections 

 will show that proficiency may be gained in reading the relief 

 without actually drawing sections, and exercises should be devised 

 to encourage this. Eventually a scale would be devised for 

 reading the relief in this way. It would be best expressed by 

 counting the number of contour intervals in a mile that is, on the 

 scale we are considering in a length of i inch on the map. Each 

 such interval signifies a grade of 100 feet in 5280 feet, or i foot of 

 height in approximately 50 feet of distance, spoken of as i in 50. 

 Five contour intervals per mile gives 500 feet in 5280 feet, or 

 i in 10, and so on. 



It will be well also to colour the contour intervals for a part, 



