1896 THE MICROSCOPE. 85 



hereafter. When used for dissecting or mounting, the 

 instrument is placed in the vertical position, on a table 

 only so high as is necessary to allow of work in a sitting 

 posture, A low power, say an inch or three inch, is 

 screwed into the nose-piece. The objective is then 

 racked down through the aperture of the principal stage, 

 and is focussed on the object lying on the supplementary 

 stage already described, a bullseye condenser, of the 

 aplanatic form suggested by Mr, Nelson, being used in 

 the case of opaque objects. 



Two wedges, or inclined planes of wood, are arranged 

 as supports for the wrists, one on either side the micro- 

 scope, or in default of these a couple of thick books can 

 be similarly used. 



It only remains to be said that with the above simple 

 arrangement, which certainly is not an expensive one, 

 any small binocular can readily be converted into a dis- 

 secting microscope, or a mounting instrument, or it can 

 be used with a four-inch or lower power, for the exami- 

 nation of animal or vegetable forms in sea water; and 

 thus the mechanical adjustments of one's larger and 

 more delicate instrument are preserved from harm. 



The advantages that may be claimed for this "adapta- 

 tion," which by the way may possibly be as well known 

 to some others as to myself, are as follows: — 



1, The use of the simple form of microscope, with all 

 the discomforts incidental thereto, is avoided, and the 

 binocular is available in place ot the single tube, 



2, The same "rack" microscope may be used, either 

 for ordinary high power work or for dissecting purposes, 

 by simply transferring the object and the sliding clip 

 from the ordinary to the supplementary stage, 



3, An instrument of relatively small size, and conse- 

 quently with short rack work, may be used with long 

 focus lenses, which otherwise can only be used in con- 

 nection with full-sized stands. 



