o HISTOET OF THE MICROSCOPE. 



Mr. Trembley, Mr. Baker, and Mr. Adams, combined to spread the 

 reputation of the instrument. 



In 1742, Mr. Henry Baker, F.RS., published an admirable treatise 

 on the microscope. He also read several papers before the Eoyal So- 

 ciety on the subject of his microscopic discoveries. In our title-page 

 we have represented an elegant scroll "pocket microscope with a spe- 

 culum," 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 vari- 

 ous 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 afiFairs of life. 



M. L. F. Delabarre published an account of his microscope 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, improved 

 his father's invention, and rendered it useful for viewing opaque 

 as well as transparent objects. This instrument, made and described 

 by him,* continued in use up to the time of the invention of the 

 achromatic improvement, proposed and made in 1815 for Amici, 

 who subsequently gave so much time to the investigation of po- 

 larised light, and the adaptation of a polarising apparatus to the 

 microscope. 



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 were very thick, and of long focus. 

 Although such considerable improvements had taken place in the mak- 

 ing of achromatic object-glasses since their first discovery by Euler in 

 1776, we find, even at so late a period as 1821, M. Biot writing, "that 

 opticians regarded as impossible the construction of a good achromatic 

 microscope." Dr. WoUaston also was of the same opinion, " that the 

 compound instrument would never rival the single.'' 



In 1823, experiments were commenced in France by M. Selligues, 

 which were followed up by Frauenhofer in Munich, by Amici in Mo- 

 dena, by M. Chevalier in Paris, and by the late Dr.^ Goring and Mr. 

 TuUey in London. To M. SeUigues we are indebted for the first plan 



• Miorosoopioal Essays, 1787. 



