830 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



I 



observed, and care was taken that the eye of the observer was in all 

 cases close to the eye-piece, so that the apparent size of the image 

 should not be affected by any variation in the distance of the eye from 

 the eye-piece. The magnifying power of the Microscope (for the 

 author's sight) was 312. 



The following table gives the results obtained, the case of the 

 shortest sight being taken as unity : — 



It will be seen that the apparent size of the images did not vary in 

 regular accordance with the variation in the distance of distinct vision. 



In the second series of experiments observers were selected who 

 were well accustomed to scientiiic observations ; M. Pire, Professor of 

 Natural Science, and MM. Niesten and Fievez, of the Eoyal Obser- 

 vatory. 



The following table gives the results, arranged according to the 

 length of vision of the observers : — 



Here the apparent sizes of the images follow exactly the order of 

 the lengths of distinct vision, and M. Montigny concludes therefore 

 that the variations that are found to exist in the case of experienced ob- 

 servers depend primarily upon the inequalities in the observer's vision. 



There are however other influences, as may be seen by the case of 

 M. Pire, whose estimations were too great in the two cases, relatively 

 to those of the other three observers. Moreover in his case the 



