134 T '1K 



AND DEVELOPMENT OF THE MICROSCOPE 



Tlii.- >v-tem of focussing was employed in a more practical form 

 I >y llart.soeker in 1 (V.I4 and was adopted by Wilson in 1702. It 

 became a very popular tin-in for the microscope in the eighteenth 

 century. 



We are indebted to Uonannus also for originating a horizontal 

 form <if microscope, \vhich is interesting and which, in a drawing of 

 the instrument. j> shown to possess a sub-sta<^e rniii /inn ml comleii.^ / 

 fitte<l I'-it/i fnriixx'nKj iiri-iinyements for ilium iimtiinj trn,i^^u,-t-nt 

 ol'jfcts. There was ure.-it convenience in using the microscope in a 

 horizontal position with a lamp and condenser in the same axis. 

 '-pecially as all the compound microscopes previously constructed 

 had l>eei i employed vertically, or had been directed towards the sky 

 for purposes of illumination. Remarkably crude as the mechanism 

 appeai-s. it is a \ery early instance of the use of what has become 

 though slowly and late on the continent a now universally acknow- 



H 



'''< 1"- Hartsoeker's simple microscope (1694). 



ledgeil optical arrangemenl indispensable for the best results, viz a 



ompo and condenser fitted with focussing mechanism for illuminating 

 ransparent objects. The picture of the entire instrument is shown 

 in d.i,'. KM. 



In Eartsoeker's microscope -the lens-carrier A IJ. fii>-. 102 (on 



', containing the lens, is serened), screws into the 



); " OQ; the thin brass plates Hand K tit within the 



SCUl out allowing them to slide,,,, the short pillars 



tl- spiral sprin- pressing them towards C D ; 



or an animalcule cage G II (hinged at a 6 to allow 



, enclosing the objects between strips of talc), 



the P^tes Band F when in position, and the " screw- 



thescrev sockel C hand regulates the focus- 



N", tits, on , second "scre^ barrel," L M, 



111 the screv -sockel of I K. This arrangement ,,I 



