98 SUMMARY OF CUERENT RESEARCHES RELATING TO 



MICKOSCOPY. 



A. Instruments. Accessories, etc.* 

 (1) Stands. 



John Cuthbert's Reflecting Microscope (1827-8) : presented by 

 the Committee of the Quekett Microscopical Club. — The earliest 

 record of a " reflecting " Microscope, that is, one in which the image is 

 formed by reflecting surfaces of speculum metal or mirrors, instead of 

 by object-glasses, is one that was suggested by Isaac Xewton to the 

 Royal Society in 1672. It is based on his well-known reflecting tele- 

 scope, and in the note to the Royal Society Newton wrote as follows : 

 " For these instruments (Microscopes) seem as capable of improvement 

 as Telescopes, and perhaps more, because but one reflective piece of 

 metal is requisite in them." 



The idea, however, was apparently not taken up, and there is na 

 record that Newton ever had this Microscope constructed. 



The next attempt at a reflecting Microscope was sixty-four years 

 later. In 1736 Barker described his " Catoptric " Microscope in the 

 Philosophical Transactions (xxxix. pp. 259-61), which was based on the 

 Gregorian telescope with two mirrors. The design, however, was bad, 

 because the small mirror is in the direct way of the object (see the 

 figure in Mayall's Cantor Lectures, Society of Arts, 1886, p. 39). In 

 1738 Dr. Smith conceived and described a much more efficient reflecting- 

 Microscope, constructed after the Cassegrainian telescope, with a hole 

 pierced through the centre of both mirrors. 



After this date we hear nothing more of reflecting Microscopes for 

 nearly a century, due no doubt to the greater convenience and improve- 

 ments in the construction of the dioptric Microscopes by Culpeper, 

 Benjamin Martin, Cuff, Adams, and Jones. 



But early in the eighteenth century, when all the attempts at pro- 

 ducing serviceable achromatic object-glasses had failed, Frauenhofer in 

 Germany, Amici in Italy, and John Cuthbert in this country, took up 

 again the subject of reflecting Microscopes in order to get rid of the 

 tioublesome spherical aberration, which at that time seemed to have 

 stopped all further improvements. 



Amici was most successful in his designs in this direction, and a 

 beautiful specimen of his work is in the Society's collection. 



John Cuthbert, acting upon Dr. Goring's advice, produced the 



♦ This BubdiviBion contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

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

 Optics and Manipulation ; (6) Miscellaneous. 



