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Single Reflecting Microscope. By Alexander Guthrie, Esq. 

 Communicated through J. Robison, Esq. Sec. 11. S. E. 



The superiority of single reflection, in adapting it to the re-* 

 fleeting telescope, for the reception of much greater magnifying 

 powers, and for its affording a greater degree of additional light 

 and distinctness, has been justly appreciated ; but, while every 

 other plan of the reflecting telescope has been metamorphosed 

 into the reflecting microscope, that plan alone, which is the best 

 adapted and the most simple, has been allowed to escape. 



Let ABCD, Fig. 1, Plate III., represent a tube furnished 

 with a field-glass m, an eye-glass w, and an eye-hole jo at the one 

 end ; and on the other a ring Aa 'Dd soldered, with its axis co- 

 incident with that of the tube. This ring is seen in section, in 

 fig. 1 ; but fig. 3. is a ground plan of it. EF, a circular plate 

 of the same dimensions as the ring, and attached to it by three 

 equal and equi-distant columns, with its plane parallel to that 

 of the ring ; E« represents one of these columns, but the whole 

 three are seen in Fig. % Let GH (Fig. 1.) represent a concave 

 speculum, set on the circular plate EF, with its axis coincident 

 with that of the tube. 



The rays of light from an object placed in the focus of paral- 

 lel rays, will, after reflection, pass on parallel to one another ; 

 but, if the object be removed back from the speculum to a cer- 

 tain point O, the rays after reflection will converge, and form 

 a magnified image of the object at I, which can be viewed to ad- 

 vantage from the eye-hole j9 by the eye-glass n. 



In order to place the object in the axis of the speculum, and 

 to adjust the focus, let ah (Fig. 5.) represent a segment of a circle, 

 of the same dimensions as the ring (Fig 3.), having a hole a in 

 the one end, of sufficient capacity to run freely on one of the 

 columns ; and a hole b in the other end, with a female screw in 

 it, and having a small spring d attached to it by rivets at the 

 one end of the spring ; and let xy represent the instrument on 

 which the object is fixed, which can be slipped in below the 

 spring in any position. Let ^y (Fig. 4.) represent the same seg- 

 ment in perspective, the female screwy receiving the spindle ab, 



