10 HISTORY OF THE MICROSCOPE. 



Mr. Baker, and Mr. Adams, combined to spread the repu- 

 tation of the instrument. 



In 1742, Mr. Henry Baker, F.R.S., published an ad- 

 mirable treatise on the microscope. He also read several 

 papers before the Royal Society on the subject of his 

 microscopic discoveries. In the wood-cut (fig. 3) at the 

 end of this chapter we have represented an elegant scroll 

 " pocket microscope with a speculum," described by him 

 as a new invention. 



In 1770, Dr. Hill published a treatise, in which he 

 endeavours by means of the microscope to explain the 

 construction of timber, and to show the number, the 

 nature, and office of its several parts, their various 

 arrangements and proportions in the different kinds ; and 

 he points out a way of judging, from the structure of 

 trees, the uses they will best serve in the affairs of life. 



M. L. F. Delabarre published an account of his micro- 

 scope in 1777. It does not appear that it was superior in 

 any respect to those that were then made in England. It 

 was inferior to some; for those made by Mr. Adams, in 

 1771, possessed all the advantages of Delabarre's in a 

 higher degree, except that of changing the eye-glasses. 



In 1774, Mr. George Adams, the son of the above, im- 

 proved his father's invention, and rendered it useful for 

 viewing opaque as well as transparent objects. This in- 

 strument, made and described by him, 1 continued in use 

 up to the time of the invention of the achromatic im- 

 provement, proposed and made in 1815 for Amici, who 

 subsequently gave so much time to the investigation of 

 polarised light, and the adaptation of a polarising apparatus 

 to the microscope. 



In 1812, Dr. Wollaston proposed a doublet in which 

 the glasses were in contact, under the name of a " Periscopic 

 Microscope." And he says, "with this doublet I have 

 seen the finest striee and serratures on the scales of the 

 lepisma and podura, and the scales on a gnat's wing." 



In the year 1816, Frauenhofer, a celebrated optician of 

 Munich, constructed object-glasses for the microscope of a 

 single achromatic lens, in which the two glasses, although 

 in juxtaposition, were not cemented together: these glasses 



(1) Microscopical Essays, 1787. 



