Illumination under Higher Poivers. By J. Smith. 3f'9 



but with powers varying from 200 to 400 diameters no diflSculty is 

 experienced in getting good results. 



I might observe that, so far as I have seen, this way of illumi- 

 nation best suits glasses of moderate aperture. 



In conclusion, I venture to express a hope that the method I 

 have described may be found of some practical use, and that, without 

 interfering in any way with other modes of illumination, it may be 

 at any rate an addition to the means of microscopic observation that 

 may be found of value to some of my fellow- workers.* 



* Siuce reading the above paper, I have througli tlie kindness of Mr. Curties 

 been enabled to try a -^ immersion of Gundhich with the greatest success ; the 

 light when properly managed being ample, and the definition very fine. 



