596 SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICROSCOPY. 



A. Instruments, Accessories, &c* 

 (1) Stands. 



Old Microscope by Pritchard. — This Microscope (fig. 64) was 

 exhibited at the June Meeting by Mr. J. T. Holder. It was made for 

 T. N. Ray in 1846, and now belongs to Mr. W. R. Reeves, of Liver- 

 pool, who kindly lent it for exhibition. It appears to be a modifi- 

 cation of Pritchard's "Solid Tripod-stand Achromatic Microsccpe and 

 Engiscope," described and figured in his " Microscopic Illustrations." 



As may be seen from the figure, it consists of a telescopic pillar, the 

 outer tube of which is screwed into a solid tripod-foot ; the inner tube 

 is surmounted by a rule-joint, to which is attached a hollow tail-piece 

 upon which slide the stage and mirror. A triangular bar, with a rack 

 cut on its posterior edge for the coarse-adjustment, passes down the 

 inside of the tail-piece, and a short arm for carrying the body is 

 attached to the top of the triangular bar by means of a screw, about 

 which the arm with the body can be rotated and secured in any required 

 position. 



The body is about 7^ in. long and 1J in. diameter inside. The fine- 

 adjustment is very simple, consisting of a micrometer screw having a 

 conical point which acts on the nose-piece against the pressure of a 

 spring. 



It may be mentioned that there is no difficulty in focusing the ^-in. 

 and the fa-in objectives by the coarse-adjustment, and this was done at 

 the Meeting, the fine-adjustment then being detached. 



The stage is mechanical, and has a transverse movement effected by 

 a screw, and a movement in arc ai right angles to the transverse one. 

 Each motion is limited to half an inch. 



The stage is composed of three plates, the lowest being fixed. The 

 middle plate carries the upper plate and its traversing screw, and is 

 pivoted on the fixed plate at the left-hand side. The milled head of the 

 traversing screw projects on the right-hand side and serves as the handle 

 of a lever, consisting of the traversing screw and the upper plates, to 

 give the movement in arc. It is thereby easy to give the stage the two 

 motions simultaneously. A so-called "safety slider-holder" is mounted 

 on the mechanical stage : it can be removed when using low powers, but 

 it is necessary when using the higher powers for focusing the objective 

 upon the object, as the body cannot otherwise be racked down sufficiently. 



* This subdivision contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



