364 



SUMMAKY OF CUKEENT EESEARCHES RELATING TO 



the length required,] it only remains to blacken the parts in the usual 

 way and fit them together. In order to permit of easy adjustment to 

 the "spot" carrier or swing arm, the ring which carries the spot is 

 sawn through at one point so that it may be " sprang " into place. 



The arc of movement is about liO^, and a stop-pin prevents any 

 undue strain on the pins of the sheaves when the upper plate is slotted, 

 or, if grooved to the edge, prevents them slipping out of their place. 



Fig. 55. 



A small piece of metal under the head of the centre pin acts as a spring, 

 and serves to keep the sheaves under even tension during their movement, 

 and at the same time prevents their displacement. 



Fig. 56. 



Figs. 55 and 56 show two methods of mounting the expanding 

 spot, flat and on a stem, as originally constructed to suit a particular 

 Microscope. 



Description of a New Reflecting Condenser by means of which 

 Ultramicroscopic Particles are made visible. — C. Reichert states * that 



* Miinchener Med. Wochenschrift, No. 51 (1906). 



