28 FIRST YEAR COURSE IN GENERAL SCIENCE 



EXERCISE XX (Textbook 239) 

 REPRESENTING ELEVATIONS BY CONTOURS 



MATERIALS : A wooden cone cut into three or more hori- 

 zontal sections, or a turnip, large carrot, or parsnip of some- 

 what conical shape; a knife; a sharp pencil; a hatpin or 

 long pin; a measuring ruler; an extra sheet of paper. 



DIRECTIONS FOR WORK: Remove the small tapering end 

 from the body selected. Cut the object across at its largest 

 part at right angles to its length, so as to give it a flat base. 



(1) Take the part which is nearest to a cone in shape and 

 measure its height; the length and width of its base. 



(2) Pass a long pin, or wire, through the body from top to 

 bottom, letting the point come through the base. Place 

 the body on a sheet of paper (not notebook paper) and 

 draw its profile, natural size. 



(3) Draw a line upon the paper completely around the 

 base. This is the contour line of the base. Press the pin 

 enough to make it prick the paper. 



(4) Remove the object, draw out the pin a little way, and 

 cut off from the bottom of the object about J of its height. 

 Replace upon the paper, so that the pin will prick the same 

 place as before. Draw the contour line of the new base. 



(5) Repeat until the object is in four pieces. Draw the 

 outline of each base and at last the outline of the top. 



(6) Replace the sections and show the place of each cut by 

 dotted lines on the profile (Case 2 above). Number the 

 lines, beginning with 0, the base. Letter the several base 

 outlines, beginning with a, the first. 



RESULTS 



Consider the body in position as in Case 6. 

 1. What is the elevation of the first section line above 

 the base? (This is the contour interval.) 



