154 THE A3IERICAN MONTHLY [Apr 



having been slightly variable, and admittedly imperfect. 



Recognizing the desirability of establishing once for all 

 a standard size, the society recently placed at the dispo- 

 sal of opticians and others who might wish to become 

 possessed of such, tools, accurately adjusted steel screw 

 gauges. These are so constructed as not to interfere 

 "with the interchangeability of previous object glasses 

 and microscope nosepieces which have been correctly 

 made to the original standard," but by means of minute 

 changes in the diameter "a slightly larger margin for 

 error in individual lenses" is allowed for. 



Microscopists would imagine that opticians would have 

 gladly made use of a means which would have enabled 

 their clients to derive so much convenience and benefit, 

 but on enquiry it will be found that so far from this be- 

 ing the case, nothing has been done to giue practical ef- 

 fect to the recommendations of the society, while the 

 firm which is noted for using the most abnormal "aniver- 

 sal" thread has shown no inclination whatever to work to 

 "the new gauge. The committee appointed last year to 

 consider the question of this gauge was composed of as 

 practical a set of men as could be selected for the pur- 

 pose, yet from want of action on the part of manufactur- 

 ers, the effort of the society seems likely to be a futile 

 one. Wake up, opticians ! do all you can to help those 

 who pay your dividends — it will be profitable in the 

 long run. 



There are several other ways in which opticians could 

 help microscopists. One matter is of first-rate import- 

 ance, and that is the adoption of an universal size or 

 * sizes for eyepieces. This has been urged on many pre- 

 vious occasions, and here again it is the optician wiio is at 

 fault, for so long ago as the year 1882 the Royal Micro- 

 scopical Society recommended the use of two sizes onlv, 

 one with a diameter of fitting of 0.92 in. for .students" 

 instruments, and the other 1.35 in. for microscopes of 



