OF ARTS AND SCIENCES. 231 



The following measurements were made out of doors : — 



Narrow green : color was visible at 35 yards. 



Narrow yellow : color was visible at .... 24 " 

 Narrow red: color was visible at 16 " 



Double Width. 



Green color visible at 56 yards. 



Red " " 28 " 



Yellow " " 40 " 



Red became invisible at 31 yards. I could see the light-colored 

 strips at 75 yards 



Triple Width. 



Green color visibla at 72 yards. 



Red " " 40 " 



Yellow " " 60 " 



The following strips were very carefully measured and cut : — 



Narrow Strips. 



Yellow color visible at 29 paces. 



Green " " 34 " 



Red " " 18 " 



I could see that there were light-colored strips at 48 paces, but 

 could not detect auy difference in the colors. The red became invisi- 

 ble at 21 paces. 



Double Width. 



Yellow color invisible at 43 paces. 



Green " " 51 " 



Red " " 23 « 



Triple Width. 



Yellow visible at 56 paces. 



Green " 67 « 



Red " 34 " 



By putting these results in close connection, we can compare them 

 to better advantage : — ■ 



