PRACTICAL GEOLOGY. 



341 



Having obtained these data by means of the theodolite, leTel, and 

 chain, the plan was plotted and transferred to a board, which formed 

 the base of the model ; this board had upright sides and ends, of 

 uniform height, nailed on to it, something like a drawer. 



f h B k 







j 



I 

















h 



i 

























e g A i 



Lign. L Plan. 



AB, Cross Section. C D, Longitudinal Section. e, f, g, h, i, k, Cross Sections. 



After the sections were plotted to the proper scale, they were trans- 

 ferred to sheets of tin and cut out, the counterpart of the section 

 forming a template ; by leaving a notch each side to rest on the upright 

 sides, this template would be used after the manner of a plasterer's 

 mould ; an inspection of the section A B will make this plain. The 



Template. 



Lign. 2., Cross Section on A B. 



surface, by means of these templates, was made exact at each line of 

 cross section, and by means of occasional levels, and from memory, the 

 portions between were filled in. The tunnel portion was cut out in 

 wood, and removeable, for the purpose of showing the position of the 

 tunnel, as shown in section A B. 



In taking the longitudinal section from C to D, the outcrop of the 

 strata was carefully marked, its dip ascertained with a clinometer, and 

 it was afterwards carefully plotted on the section, as shown in the 



