MICROSCOPIC OBJECTS. 197 



are very apt to do in instruments having deeper eye- 

 pieces. This will be found a great advantage in many 

 cases, as the powers of a megaloscope are frequently 

 those best adapted for drawings, giving general views of 

 objects. 



The body of the instrument I am describing, and which 

 is now before me, is made of a very stout brass tube, so 

 that when the glasses are in their places, it weighs three 

 poimds, which requires the stand to be stout in pro- 

 portion. I should be very much disposed to make the 

 tube of that kind of pasteboard, and in the same way, 

 that I have seen the tubes of common Dutch telescopes 

 made, which answer sufficiently well. Moreover, I 

 should have both the eye- and object-glasses set m wood, 

 instead of metal, as they are in the Dutch spy-glasse& 

 aforesaid. This arrangement would make the body so 

 hght that the stand of any ordinary engiscope might be 

 adapted to it. Moreover I would make the main tube 

 3 inches ui diameter instead of 2|-, by which the field of 

 view might be enlarged ; for no large field of view can 

 be obtained ^^dthout a large field-glass, and consequently 

 a large body : that of the present instrument is only of 

 the usual size of that of engiscopes with single field- and 

 eye-glasses, and if it could be made larger, it vv^ould 

 certainly be much more agreeable. 



or that in contact with the eye-glass, which projects and is not in 

 action, may be cut away for convenience. I think, moreover, that 

 a prism of 60° reflects much the same quantity of light whether it 

 it is silvered or not on the reverberatory surface. 



