180 



Journal of Applied Microscopy. 



OBSERVER 2. 

 Time unlimited. 



Time limited. 



Metiiod. 



C. 



SettinR-s 



Settings 



P. E 0.49 0.28 0.25 



Each method in alternation. 



Method. 



Settings 



OBSERVER 3. 



Time unlimited. 

 Method. 



Settings 



81.5 

 78.0 

 76.0 

 76.5 



77.8 

 81.5 

 74.0 

 74.5 

 79.0 

 78.5 

 81.2 

 78.2 



19.5 

 23.0 

 21.5 

 21.0 

 19.8 

 22.5 

 22.0 

 23.2 

 22.0 

 22.5 

 23.0 

 22.8 



89.0 

 87.5 

 88.0 

 89.5 

 91.2 

 87.5 

 89.5 

 92.0 

 92.5 

 91.5 

 91.0 

 91.4 



0.54 



p. E 0.26 0.19 0.12 0.19 



D. 



80.0 

 77.5 

 80.0 

 77.8 

 78.5 

 81.0 

 80.2 

 80.5 

 78.0 

 80.0 

 78.5 

 79.8 



Method. 



A. 



B. 



C. 



Settings 



Settings 



90.0 

 93.5 

 96.8 

 93.0 

 91.0 

 94.5 

 92.2 

 97.0 

 92.2 

 93.5 

 94.5 

 96.2 



32.5 

 34.2 

 30.0 

 34.2 

 29.0 

 29.0 

 33.2 

 32.0 

 33.5 

 33.0 

 33.8 

 36.0 



3.5 



7.2 

 5.0 

 5.5 

 6.8 

 5.8 

 6.0 

 5.0 

 7.5 

 5.2 

 8.8 

 3.8 



P. B. 



0.45 0. 



OBSERVER 4. 



Time unlimited. 



Method. 

 Settings 



Each method in alternation. 



Method. 

 Settings 



C. 



p. B 0.39 0.23 0.35 0.23 p. B 0.46 0.29 0.31 



D. 



89.0 

 88.8 

 88.2 

 86.-5 

 85.8 

 80.8 

 86.0 

 88.8 

 88.2 

 90.0 

 90.2 

 90.5 



0.76 0.12 



D. 



p. E 0.51 0.09 0.11 0.49 



As might have been expected, an in- 

 spection of these tables does not indi- 

 cate any single method as possessing 

 decided advantages. The personal equa- 

 tion is a very important factor. There 

 are certain conclusions, however, which 



it would seem may be drawn from this 

 work: 



1. With one exception, method A (in- 

 tersecting wires) gave the largest prob- 

 able error, and may easily be classed as 

 the poorest method. 



