166 MICROSCOPIC ILLUSTRATIONS. 



microscope and a telescope pass into each other by in- 

 sensible degrees : a species of telescope can always be 

 made of the former, and a kind of microscope of the 

 latter, but both of the most execrable kind. To this last, 

 namely, a short spy-glass, or perspective glass, with a 

 long pull-out tube, so as to permit it to adapt itself to 

 rays which are considerably divergent, the term Engi- 

 scope has already been applied by Martin and others, but 

 I think most unwarrantably, for such an execrable piece 

 of trumpery is wholly unworthy of a separate existence, 

 or a separate name ; it is just as easy to make a piece of 

 velvet of an ass's hide as to make an object-glass which 

 shall answer both for a telescope and a compound mi- 

 croscope, be its focus what it may. The only veritable 

 engiscope is the latter instrument, with an objective- glass 

 truly adapted to act with divergent rays ; a short tele- 

 scope may be made of six inches focus, and a long com- 

 pound microscope with an object-glass also of six inches 

 focus, but the construction of each must be utterly 

 different, or they will only nominally be what they are 

 called. 



I therefore hope that I shall be allowed (as I have 

 reformed and revolutionized both the optical and mechanical 

 structure of microscopes] to change their names also, and 

 shall therefore take the liberty of using the term engi- 

 scope, as aforesaid, instead of compound microscope, 

 and retaining the expressions microscope or simple mi- 

 croscope, for convenience sake, to denominate what is now 

 called a single microscope, in opposition to a compound. 



