572 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 104. 



as the silk fibres, and tlie latter should therefore be made to 

 coincide with the centres or corresponding edges of the ruled lines ; 

 it is, however, impossible to attain perfect accuracy unless tbe 

 stage-micrometer be much more truly divided than those in ordinary 

 use. 



Nelson's New Nose-piece Adapter.— Mr. E. M. Nelson has 

 , devised a new form of adapter (fig. 104), for rapidly changing objec- 

 tives, founded on the principle of the 

 bayonet-joint. A collar is screwed upon 

 the objective furnished with three radially 

 disposed projecting pins placed at equal 

 distances apart. The adapter, which screws 

 into the nose-piece, is provided with three 

 internal annular slightly sloping grooves 

 and three vertical notches. The pins are 

 slipped up the notches and a partial turn 

 given to the objective secures it firmly in 

 place. 



Curties' Nose-piece Adapter. — Fig. 105 

 shows the first rough model of this device, 

 which is designed as an improvement on 

 Pease's " Facility " nose-piece {ante, pp. 

 425-6). 

 The nose-piece screws on the Microscope by the usual " Society " 

 screw shown at the top, and may remain there permanently. A is 

 a box, or cap, fitting over three equal seg- 

 ments B of a ring having the " Society " 

 screw on the inner surface. Each segment 

 has on its upper edge a grooved tooth work- 

 ing against a flat spiral, and on its lower 

 edge a guide-piece C passing through a 

 slot on the edge of A. The rotation of A 

 acting on the guide-pieces forces the seg- 

 ments to travel in the spiral, in one direc- 

 tion moving them towards the periphery, 

 consequently expanding their circle, so that 

 the objective may be slid in, and in the other direction causing them 

 to move towards the centre when they grip on the threads of the 

 objective. E is a fixed pin to limit the rotary motion of A. 



With this device no alteration is required to the usual brass-work 

 of the objectives. Any objective having the " Society " screw can be 

 slid into the nose-piece at once, when one-sixth of a turn of A to the 

 left will cause the segments to grip it in place, whilst the reverse 

 movement will release it. 



The objections to the nose-piece appear to us to be, 1st, the diffi- 

 culty of centering, — the segments have to be made so loose, that 

 there can be no good centering ; and, 2ndly, the liability to injure 

 the thread of the objective through there being no provision to insure 



Fig. lOf). 



