The rods are cut to lengths equal to the surface elevations of wells on the 

 vertical scale selected, plus an amount equal to the depths of the holes into which 

 they will be mounted. The formations penetrated by the wells are represented 

 on the rods by bands painted in different colors. 



After the rods are cut, painted, and set in their respective locations, the 

 formation tops from well to well are shown by strings colored the same as the 

 formations which they represent, as indicated in Figure 24-46. When all the 

 rods are connected with the colored strings, the planes of the formations can 

 be seen in their approximate relationships to one another. Of course, this 

 illustrative method does not permit showing the curved surfaces of the structures, 

 but it does suggest them in the sloping planes of which the strings are elements. 



Solid Models 



A solid relief model of a structure can be made in much the same way as a 

 topographic relief model, if there is a good structural contour map of the area. 



The contour map is used as a pattern. Since the map will be cut during the 

 construction of the model, several copies should be on hand. Sheets of pressed- 

 fiber wallboard are cut with a coping saw along each contour line, as shown 

 in Figure 24-47/?. When the first sheet is mounted on the base, the next higher 

 contour is transferred to it, as shown by the dashed line in the figure cited. 

 This may be done with one of the uncut maps and carbon paper. The transferred 



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Figure 24-46. Peg model of a simple dome. 



506 



