JONES'S MICROSCOPE 



Its date was 1798, and is seen in fig. 112, which is taken from the 

 original figure in Adams's * Essays 011 the Microscope.' 



The base is a folding tripod, and the stem inclines upon a 

 compass-joint on the top of the pillar. Mr. Mayall justly remarks 

 that this was the best system devised up to this date. The arm 

 carrying the body- 

 tube can be rotated 

 on the top of the limb 

 E, and is also pro- 

 vided with a rack and 

 pinion D. An extra 

 carrier, W, is pro- 

 vided for special pur- 

 poses pivoting at S, 

 so that objects will 

 remain in the optic 

 axis though the stage 

 be moved in arc. 

 There are also clips 

 provided for the 

 stage. There is a 

 condenser at U, 

 which slides on the 

 stem by the socket u. 

 The mirror also slides 

 on the stem. There 

 is provided a rotating 

 multiple disc, P, of 

 object-lenses, and a 

 brass cell contains a 

 high power, of .,',, or 

 ^o inch focus, which 

 on the removal of the 

 lens- disc can be 

 screwed into the 

 nose-piece. 



There were also 

 designed some inte- 

 resting forms of re- 

 flecting microscopes, 

 to the details of which 

 we can afford no 

 space, their influence 

 having been of no 

 value in the develop- 

 ment of the microscope as we know it. There was a reflecting 

 microscope suggested by Sir Isaac Newton in 1672, and one was 

 devised on the principle of the Gregorian telescope by Barker in 

 1 736 ; another of the Cassegrainian form was made in 1738 by Smith, 

 which was, perhaps, the most perfect of the Catoptric forms. 



An outline of its construction and the path of the light-beams is 



L 



JONES'S MOST IMPROVED COMPOUND 



MICRO Si-Ota AND AfPARATVX. 



Fi G ll2 (1798). 



