Microscopical Essays, X j 



at the fourth length, one hundred and forty-three times. It does 

 not appear that E. Divini varied the object lenfes. 



Philip Bonnani publifhed an account of his two microfcopes in 

 1698 ; * both were compound ; the firfl was funilar to that which 

 Mr. Martin publifhed as new, in his Micrographia Nova,f in 

 1712. His fecond was like the former, compofed of three 

 glafles, one for the eye, a middle glafs, and an object lens: 

 they were mounted in a cylindrical tube, which was placed in an 

 horizontal pofition ; behind the ftage was a fmall tube, with a 

 convex lens. at each end ; beyond this was a lamp ; the whole ca- 

 pable of various adjuftments, and regulated by a pinion and rack ; 

 the fmall tube was ufed to condenfe the light on the object, and 

 fpread it uniformly over it according to it's nature, and the mag- 

 nifying power that was ufed. 



If the reader attentively confiders the conftruclion of the fore- 

 going microfcopes, and compares them with more modern ones, 

 he will be led to think with me, that the compound microfcope 

 has received very little improvement fmce the time of Bonnani. 

 Taken feparatcly, the foregoing conftruclions are equal to fome 

 of the moll famed modern microfcopes. If their advantages are 

 combined, they are far fuperior to that of M. Dellebarre, not- 

 withstanding the pompous eulogium affixed thereto by Meff. De 

 L'Academie Royale des Sciences, t 



C From 



* Bonnani Obfervationes circa viventia, &c. 

 i Micrographia Nova, by B. Martin, 4to. 



+ Memoires fur les Differences de la Conflru&ion et des Effets du Microfcope, 

 de M. L. F. Dellebarre,, 1777. 



