308 HOW TO SEE WITH THE MICROSCOPE . 



with condensers of very small diameter, several of 

 these of varying focal lengths were fitted to the same 

 mounting. Either glass could thus be used at pleasure. 

 The mounting was conical and the base being also of 

 small diameter, say about one-fifth of an inch, our idea 

 was by this arrangement to keep the angle of the con- 

 densing lens as low as possible, and by the peculiar 

 form of its mounting to illuminate as little as possible 

 of the object and with an extremely acute cone of light 

 and at the same time, allowing sufficient lateral range 

 that the instrument might be placed in as oblique posi- 

 tion as possible. The idea seemed theoretically sound, 

 and we have spent much time in the experiments hoping 

 to give our readers something of value, but we were 

 doomed to disappointment. (Not the first experiment 

 of ours which has failed). The instrument is very 

 troublesome to use, requiring often some little time to 

 coax the light through the little cone, and when once 

 obtained, the slightest movement of the mirror will 

 destroy what has been done. Nor when doing its best 

 were the results any better than those obtained by the 

 Gundlach, or Beck cheap inch which has already been 

 recommended for general condensing purposes. We 

 still believe that some improvement will be made in the 

 direction of our experiment, and hope that other ob- 

 servers will make similar efforts until further success 

 shall be secured. 



