274 THE CANADIAN NATURALIST. [Sept. 



ON MICROSCOPIC ACCESSORIES. 



By J. Baker Edwards, Ph.D., F.C.S., 



Hon. Sec'y Montreal Microscopic. Club, and Cor. Mem. Liverpool Micro. Cltib and New 

 York Microscopic Society. 



Next to the possession of a good, solid, smoothly-working stand, 

 with good powers and good illumination, is the desire for the 

 acquisition of those useful accessories which the zealous micro- 

 scopist soon finds are essentials to his progress in practical study. 

 Of these I shall first notice simplifications which amount to 

 pcTir.anent improvements. Thus the shutter or graduating 

 diaphragm is an improvement likely to supersede the rotating 

 diaphragm beneath the stage ; and the adjusting side-light as a 

 parabolic reflector is a useful substitute both for the bull's-eye 

 condenser and the various Lieberkuhns. The orthobcopic eye. 

 piece, in its double service as an achromatic condenser, is also 

 a valuable and economical accessory. I have already stated that 

 the binocular prism is an essential to the best form of stand, and 

 is entitled to a higher place in the estimation of the working 

 student than a mere accessory. 



The new rotating glass stages of either Messrs. Crouch or Collins 

 certainly accessions to the instrument and can be recommended 

 to those who do not care about the expensive mechanical stage. 

 The movement is smooth and true, and the fingers may soon 

 become educated so as work the object with all the precision 

 desired. 



A rotating diaphram, furnished by Crouch or Collins, also gives 

 all the effects of the dark well and oblique illuminations. 



The parabolic condenser of Wenhani is an invaluable illumina- 

 tor for foraminifera, polycystina, and transparent injections. 



The camera lucida, lever compressorium and object glass 

 reflectors may, I think, be consideicd as luxuries, not at all 

 essential to the student. So also the '• Erecting Eye-piece," 

 although invaluable under exceptional circumstances, may be 

 generally dispensed with, as, for ordinary dissections, the bin- 

 ocular folding stand, called the " Collins' Lawson Dissector," 

 holds the preference. 



Every real student should procure at least a stage micrometer, 

 and he will probably not regret the possession of a " cobweb 



