53 



MAGNIFICATION AND DRAWING. 



Thus, suppose the 5 spaces of the scale of enlargement given with a 

 drawing were found to measure 25 millimeters and the spaces on the 

 micrometer were T oTr tn millimeter, then the enlargement would be 

 25 -i- T £u = 500. That is, the image was drawn at a magnification of 

 500 diameters. 



If the micrometer scale is used with every drawing, there is no need 

 of troubling one's self about the exact distance at which the drawing 

 is made, convenience may settle that, as the special magnification in 

 each case may be determined from the scale accompanying the picture. 

 It should be remembered, however, that the conditions when the scale 

 is drawn must be exactly as when the drawing was made. 



