Microscopical Essays, 



which means, the aberration of light from the figure is in fome 

 meafure corrected, and the apparent field increafed. 



Of the Solar Microscope, 



In this inftrument, the image of the object is thrown upon a 

 fcreen in a darkened room. It may be confidered under two 

 diftin6l heads : ill, the mirror and lens, which are intended to 

 reflecT: the light of the fun upon the object ; and 2dly, that 

 part which conftitutes the microfcope, or which produces the 

 magnified image of the object, Fig. 10, Plate I. Let NO repre- 

 fentthe fide of a darkened chamber, GH a final! convex lens, 

 fixed oppofite to a perforation in the fide NO, A B a plane 

 mirror, or looking-glafs, placed without the room to reflect the 

 folar rays on the lens CD, by which they are converged and con- 

 centrated on the object fixed at E F. 



2. The object being thus illuminated, the ray which proceeds 

 from E will be converged by the lens GH to a focus K, on the 

 fcreen L M; and the ray which comes from F will be converged 

 to I, and the intermediate points will be delineated between I and 

 K ; thus forming a picture, which will be as much larger than 

 the object, in proportion as the diftance of the fcreen exceeds 

 that of the image from the object. 



From what has been faid, it appears plainly, the advantages we 

 gain by microfcopes are derived, firft, from their magnifying 

 power, by which the eye is enabled to view more diftincUy 

 the parts of minute objects : fecondly, that by their afTiftan.ce, 

 more light is thrown into the pupil of the eye, than is done with- 



.G out 



