US 



of a Gtobgual J/*/. In order to show 

 the application of the foregoing observations, two diagrams 

 27 and 28) are here given. In Fig. 27 an attempt 

 is made to convey some idea of the way in which the 

 jo pared data are compiled and recorded in the construe- 

 <>f a geological map. The shaded parts of that 

 resent what is actually seen by the geologist ; 

 over the blank portions he is supposed to have been 

 c to find any rock in situ. Fig. 28 shows the map 

 as filled in and completed from these data. I shall 

 occasion to make frequent references to these maps in 

 what follows. 



It will be noticed that most of the observations occur 

 along the stream-courses, these IH in^ the most frequent 



1 lines of section. At each point where the 

 strata has been taken, an arrow and number mark the 

 and angle. The more im)>ortant or strati- 

 graph ically serviceable beds have their outcrop marked 

 in decided lines where it is actually seca When the 

 same stratum can be recognised in two parallel or adjacent 

 streams or valleys, the outcrop may be drawn across the 

 intervening ground, which of course should itself be 

 searched for traces of the desired line. Where there can 

 be no doubt as to the direction and position of the out- 

 crop, it may be drawn as a continuous line or band. 

 Where, however, though it is known to occur within 

 certain limits, some doubt may exist as to its exact 

 position, it should be expressed by broken or dotted 



nttigrapJu'fat order of Sucttssio*. It 

 will be seen from the map that in the streams at the 



