1074 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



field. (In making this test it is as well to use the same eye-piece on 

 each tube.) 



6. When the carrier of the prism is pushed home, the edge of the 

 prism should exactly bisect the back of the objective. Fig. 247 shows 

 the picture in the left-hand tube when the prism is not pushed in far 

 enough. When the prism is pushed in too far the dark patch would 

 be seen on the opposite side of the right-hand tube. 



7. The diaphragms in the eye-pieces should be of the same size 

 (fig. 2i8). 



Fig. 243. 



Fig. 244. 



Fig. 245. 



Fig. 246. 



The best way to find out if the fields are exactly superimposed is 

 to blink or wink rapidly with each eye alternately." (Mr. Nelson's 

 remarks apply to the Wenham Binocular only.) 



Position of Objects with the Binocular. — Mr. E. M. Nelson, 

 considering that the binocular Microscope does not give images so 

 good as the monocular, has endeavoured to find out the cause and to 

 remedy it if possible.* 



He obtained a Wenham prism of good quality and had it properly 



* Journ. Quek. Micr. Club, ii. (1885) pp. 198-200. 



