Microscopical 



Es s a y s. 



2 3 



M. L. F. Dellebarre publifhed an account of his microfcope 

 in the year 1777. It does not appear from this, that it 

 was fuperior in any refpecl to thofe that were then made in 

 England, but. was inferior in others ; for thofe publifhed by my 

 father in 1771, poffeffed all the advantages of Dell ebarrc s m a 

 higher degree, except that of changing the eye glafles. 



In 1784, M. /Epimis publifhed a defcription of what he 

 termed new-invented microfcopes, in a letter to the Academie des 

 Sciences de St. Pcterfburg; * they are nothing more than an ap- 

 plication of the acromatic perfpeclive to microfcopic purpofes. 

 Now it has been long known to every one who is the lead verfed 

 in optics, that any telefcope is eafily converted into a microfcope, 

 by removing the objecl: glafs to a greater diftance from the eye 

 glaffes j and that the diftance of the image varies with the diftance 

 of the -objecl: from the focus, and is magnified more, as it's 

 diftance from the objecl; is greater: the fame telefcope may, 

 therefore, be fuccemvely turned into a microfcope, with different 

 magnifying powers, Mr. Martin had alfo {hewn, in his defcription 

 and ufe of a polydynamic microfcope, how eafily the fmall acro- 

 matic perfpeclive may be applied to this purpofe. Botanifts. 

 might find fome advantage in attending to this inftrument • it 

 would affift them in difcovering fmall plants at a diftance, and 

 thus often fave them from the thorns of the hedge, and the dirt of 

 a ditch. 



Fig. i, Plate III. reprefents the improved lucernal microfcope. 



* Defcription des Nouveaux Microfcopes, invcntes par M. iEpinus., 



