

326 STRUCTURAL AND FIELD GEOLOGY 
the ground, that we learn to appreciate the intimate relation 
that obtains between surface features and geological structure. 
Everyone is prone to exaggerate slopes—even experienced 
artists frequently do so, especially in the case of mountains— 
and the young geologist who neglects to train his eye by 
frequent section drawing on a true scale, is not likely to 
escape this common failing. The beginner will find it 
excellent practice to draw topographical (not geological) 
sections in all directions across some of the hilly tracts 
represented on the large 6-inch maps of Scotland. He will 
doubtless be surprised to see how inconspicuous many heights 
appear when drawn to scale, how relatively gentle are the 
undulations of the surface even in a mountainous tract. In 
the same way he will recognise that the deep basins occupied 
by our larger lakes when seen in their true proportions are 
mere shallow pans or troughs. Loch Ness, for example, is 
780 feet deep, but then it is not less than 221 miles long, so 
that the length is 152 times greater than the depth. 
Of course it is not always possible to plot geological 
sections on a true scale. If the region to be illustrated be of 
great extent, say 100 miles across, it is obvious that we must 
generalise both the topography and the geology. Even in 
such cases, however, it is important to indicate as clearly as 
may be the leading surface features of the region andthe 
relation of these to the geological structure. A _ similar 
remark holds good with regard to all sketch-sections. Should 
the heights and slopes of the land be so inconspicuous as to be 
barely perceptible when drawn upon a natural scale, it is often 
necessary to exaggerate them in order to show their relation 
to the internal structure. The exaggeration, however, should 
not be so pronounced as to amount to positive distortion. 
In running a geological section, care should be taken to 
draw it as nearly as possible at right angles to the strike. If 
the strata be inclined in the same direction throughout a 
district, the section will necessarily follow a straight line. 
But should the strike vary from point to point, the line of 
section will be correspondingly sinuous or zig-zag. Reference 
to Plate LVI. will show how frequently the direction of a 
section-line must change, when it is desired to bring into one 
connected view the general geological structure of a whole 

