194 



THE GUIDE TO NATURE 



MICROSCOPE STAND MADE P.Y R 

 BOSTON. 



J!, TOI.LES, 



by George Adams of London about 1790. 

 The drawer in the base of the stand con- 

 tains several accessories of the period, in- 

 cluding a "fish-plate" for examining the 

 circulation of the blood in the tail of a 

 fish or in the web of a frog's foot. There 

 are also several ivory "sliders" contain- 

 ing various objects mounted dry. 



The history and evolution of the mi- 

 croscope are exceedingly interesting and 

 would require much space to go into de- 

 tail, therefore only a few of the most im- 

 portant points will be noted in this brief 

 article. 



Microscopes are either simple or com- 

 poimd, the former consisting of a single 

 lens or system, while the compound mi- 

 croscope contains two or more lenses or 

 combinations, the image formed by the 

 objective at the lower end being magni- 

 fied by the eye-piece at the upper end of 

 the tube. 



It is recorded that crystal lenses or 

 magnifiers were used by Roger Bacon, a 

 Franciscan monk, in 1276, and he may be 

 considered the inventor of the simple mi- 

 croscope. 



The discovery of the compound micro- 

 scope has been attributed to Hans and 



Zacharias Jaussen, spectacle makers of 

 Aliddleburg, Holland, between 1590 and 

 1609, although there are grounds for be- 

 lieving that Galileo, the inventor of the 

 telescope, was also the inventor of the 

 compound microscope at about this same 

 period. 



During the seventeenth and eighteenth 

 centuries, many varieties of the com- 

 pound microscope were made, such as 

 Campani's microscope (1660); Hooke's 

 microscope (1665); Divini's (1668); 

 Bonanni's (1691) ; Marshall's (1704); 

 Hertel's (1716); Joblot's (1718); Cul- 

 peper and Scarlet's (1738); Martin's 

 (1780); George Adams' (1771) and 

 Jones' (1798) ; 



The result obtained with the compound 

 microscope of that period, on account of 

 poor definition and loss of light, were far 

 from satisfactory, and the simple micro- 

 scope w^as thought by many observers to 

 be more reliable than the compound in- 

 strument ; and indeed all the wonderful 

 discoveries of Leeuwenhoek (born 1632, 

 died 1723) sometimes referred to as "the 

 father of microscopy", were made with 

 the simple microscope consisting of single 

 lenses ground by himself. 



When the achromatic principal was fin- 

 ally applied successfully to the compound 

 microscope about 1825, great advances 

 and important discoveries were made, and 

 during the following fifty or sixty years, 

 the microscope stand, objectives and ac- 

 cessories were developed to a high state 

 of perfection both in this country and in 

 Europe. ^Microscopical societies were 

 formed in every community and great in- 

 terest was taken by amateurs in "fight- 



rWELVE MICROSCOPIC OBTECTIVES MADE BY 

 R. B. TOLLES, BOSTON. 



