STRATA 10$ 



- therefore the position of the boundary 

 must be inferred, the surveyor will followthe analogies 



.rid run his boundaries with the sain. 

 of flowing lines which he sees them to possets where 

 they can be actually examined Two men may map the 

 same piece of ground <juitc correctly as regards its general 

 Uu the map of the one will show by the com- 

 , <>f its lines .iii.l the fidelity with which they follow 

 the varieties of the surface configuration, how faithfully and 

 skilfully the work has been done ; \\lnle the map of the 

 other will indicate that its author, though marking cor 

 general strut tu re, has failed to recognise, or, at 

 least, to express the relations of that structure to external 

 form. ; mer map will in most cases be a far more 



. as well as accurate production than the latter. Not 

 only in such simple work .is the tracing of horizontal M 

 but in all the details of geological map-making, t 

 eye and hand have scope to show their presence ; to the 

 great advantage of the maps to which they are applied. 



Dip. Instead of lyin^ quite flat, 



howt-N rocks are usually inclined to the 



mation, called their i///, is measured 



i MI. dip coocMbd by wprtckl dkrarbuM of tlw *mu. 



as to its direction by the compass, as to its angle by the 

 clinometer. In determining these points it is always 

 desirable to see more than a mere projecting edge of 

 rock, for sometimes what seems to be the dip in such a 



