294 



ACCESSORY APPARATUS 



adapters to equalise the length of the objectives, so when a change 

 of objective- i> made little change of focal adjustment is required. 

 Ki L:-. _.'!''>. -'.'i7 show the nature of this arrangement. In Kelson's 

 changing Dose piece a small ring with three studs is screwed on to 

 the objective; a nose-piece is screwed on the microscope, having 

 t hree slotsand three inclined planes. Therefore, by placing the studs 

 into the .-lots and giving the objective a quarter of a turn, the 

 Muds run up the inclined planes, thus causing the flanges to ' face 

 up' tightly. 



Mr. Nelson has pointed out a far better and simpler method 

 which dispen-es with all extra apparatus. 



Three port ions of the thread in the nose-piece of the microscope 

 it >elfai-e cut away, and also three portions on the screw of the 



Pro. 23C. Xei^sV sliding-objective 

 changer, with objective in 



FIG. 237. The objective detached from 

 the body-slide. 



objective. Those portions where the thread is left on the objective 

 pass through those spaces in the nose-piece where it has been cut 



away. The screu engage.- j ii.-t as i f i he \\ hole ,-crew were there, and 

 the objective faces up in the usual manner. This plan ill 110 way 

 injure.- either the microscope or 1 he object ives for use i n 1 he ordinary 

 way; thus uncut objective.- will screw into the nose-piece, and cut 

 objectives will screw into an uncut nose piece. This plan is similar 

 to that employed in dosing the breech of guns, and it was seeing one 

 Of them in ISS-J which suggested fco .Mr. Nelson to adapt the same 

 principle bo the microscope. Sub-djueiitly it has been found that 

 in IHC.'.I Mr. James Vog.-in had proposed much the same plan, only 

 ing away two portion- instead of three : it is curious that such 

 an excellent j,!,.;, \ V as allowed to drop. 



An "/m///.v/,,,/ nose piece j> th.-it \\hich carries a Nicol's analysing 



