208 The Ohio Journal of Science [Vol. XVII, No. 6, 



For enlarging drawings there are several methods possible. 



1. Take an important axis and erect ordinates. Assume a 

 scale of magnification and find the length of the axis magnified 

 and locate the ordinates also magnified. This method reversed 

 will also serve in case one wishes to reduce the dimensions of 

 an object. 



2. Use the method of small squares, drawing them faintly 

 but definitely over the drawing to be enlarged, or outline the 

 original drawing on transparent (tracing) paper and draw the 

 squares over this outline. 



Then on your chart draw squares whose dimension is the 

 number of times larger than the small squares that you wish 

 the drawing magnified and redraw on the new area, placing the 

 points and lines on the large squares in positions corresponding 

 to those shown in the small squares. 



3. A modification of this method is to use a gelatin sheet, 

 draw a net of squares on it with a sharp point. This may be 

 placed over the picture and the outline traced as in No. 2. 



If such a transparent outline be elevated and a small aper- 

 ture arranged above it so that the eye looks from what is essen- 

 tially one point the outline can be traced as projected on the 

 chart on the drawing table. Large drawings can not be traced 

 in this way because of one's inability to reach lines beyond a 

 certain distance from the eye. 



4. ■ Use a Pantograph or multiplying apparatus. A good 

 one costs $6-$8, the cheaper ones are useless. 



5. By using a reflectoscope if you have one, you may 

 project your diagram or drawing on the drawing paper pinned 

 to the screen and outline it perfectly. 



The order of making a chart is as follows: 



1. Lay out the chart. 



2. Copy figure with faint lines of a fairly soft pencil (3 H). 

 Clean with a sponge rubber which will not spoil the grain of the 

 paper if water color is to be used. 



3. Put in shades. This will be described in the next section 

 of the paper. For large shades use absorbent cotton and the 

 color, and it will give a fairly evenly shaded area. 



