What did our Forefathers see in a Microscope ? 431 



measurements of the six objectives taken from an excellent 

 example * of one of these Microscopes : — 



Whole Microscope, with No. 6 and back lens, focus * 33, power 

 29 "9; without back lens, focus 0*29, power 34*1. Those 

 marked (a) were measured with the 5^-in. focus-lens removed 

 from the top of the " pipe." The action of this lens, by reducing 

 the power and increasing the aperture, increases the optical index, 

 and consequently improves the Microscope. 



Jones added to Martin's Microscope a biconvex lens of 2-in. 

 focus as a substage condenser,f and in this condition the dioptric 

 compound Microscope remained until it was achromatised. The 

 origin of the " pipe " is of interest. It first appears in the " New 

 Constructed Double Microscope," made by Cuff, 1744, for the 

 purpose of adapting Dr. Lieberkiihn's mirror J to a compound 

 Microscope, and it was the first compound Microscope to have 

 this mirror. § Benjamin Martin, in 1770, copies this form of 

 " pipe " and lieberkiihn, and places his back lens at the top of it. 

 However, in 1776, the "pipe" is discarded, the end of the body 

 tube is made conical with an ornamental curve, the back lens is 

 retained at the base of the cone, and the lieberkiihn is mounted 

 upon a separate holder. Adams, in 1771, published a book of 

 plates of Microscopes in which Cuff's models are figured. We 

 may, therefore, assume that Cuff had either died or retired from 

 business in 1770. The Microscopes made by Benjamin Martin 

 with Cuff's "pipe" may be dated between 1770 and Martin's 

 death in 1782. The screw on Martin's " pipe " passed on to 

 Tulley, who used it for the first achromatic objective of the Lister - 

 Tulley Microscope! of 1826, and from thence to James Smith, 

 from him to Richard Beck, and from him to the Microscopical 



* Benjamin Martin (circa 1770). See this Journal, 1898, p. 474, fig. 81. 



t See this Journal, 1899, p. 326, fig. 73 (unsigned, but exactly similar to 

 Benjamin Martin's "New Universal Microscope," 1776). Presented to the 

 R.M.S. by the late Dr. Dallinger. 



% Called after Dr. Lieberkiihn, because, in 1740, he brought it into general 

 use. It had been previously described by Descartes (1637), and used by 

 Leeuwenhoek, circa 1673. 



§ Journ. Quekett Micr. Club, 1898, ser. 2, vii. p. 116, fig. 23. Presented to the 

 ft.M.S. by Mr. C. L. Curties. || See this Journal, 1900, p. 551, fig. 146. 



