84 FIELD GEOLOGY. 



Filling in Geology. The geological details are filled 

 in by aid of the boundary lines on the map, of the par- 

 ticulars observed in exposed sections and ascertained 

 from wells or borings, and to a great extent by inference 

 from such evidence. The lines of boundary and outcrop 

 are scaled off from the map, or their position noted in 

 the measurements along the line of section levelled, the 

 beds drawn with the proper inclination, true or apparent 

 dip as the case may be, and with all known faults, flex- 

 ures, and contortions dotted lines only being used 

 where the details are uncertain. In this operation the 

 table given at page 50 will be found of service, but care 

 must be taken to allow for unevenness of the 

 ground, by drawing a horizontal line to work from 

 through the point at which the calculations are to be 

 applied. 



Apparent Dip. Frequently the line of section will 

 run not in the direction of the dip, in such cases the in- 

 clination of the beds must be shewn as it would appear 

 in a section cut through them along that line. The 

 difference can be found by calculation, but is more 

 readily ascertained by diagram, or on reference to a table 

 constructed by the late Mr. J. B. Jukes, and published 

 by him in the Appendix to the " Geology of the South 

 Staffordshire Coal-field." Mems. Geol. Survey. It is 

 given also in an abridged form in his " Manual of 

 Geology," with the addition of some valuable hints on the 

 construction of geological sections. 



In the article previously quoted (p. 49) Mr. Dalton 

 gives a method of finding the apparent inclination in a 

 direction oblique to that of the true dip. 



"Problem. To find the apparent angle in any re- 



