Dr* fVollastorCs Microscopic Doublet. 251 



condensing lenses, under the stage, are capable of producing the 

 effect recommended by Dr. Wollaston, much in the same man^ 

 ner as his own illuminating apparatus, used in his own way, as 

 directed in App., par. 3, does ; for it is of little consequence to 

 what space the illumination is confined, whether by the image 

 of a perforation, or by a stop placed close behind the object ; 

 because no microscope can collect or bring rays to the eye, 

 which are without the pale of its field of view, the field-bar, or 

 aperture of the lens (if a simple microscope) excluding all the 

 extraneous light. 



Par. 4. *• With respect to the apparatus for magnifying, notwithstand- 

 ing the great improvements lately made in the construction of micro- 

 scopes, by the introduction of achromatic object-glasses, and the manifest 

 superiority they possess over any single microscope, in the greater extent 

 of field they present to view at once, whereby they are admirably adapted 

 to make an entertaining exhibition of known objects. Hardly [any one 

 of the compound microscopes which I have yet seen is capable of ex- 

 hibiting minute bodies with that extreme distinctness which is to be 

 obtained by more simple means, and which is absolutely necessary for an 

 original examination of unknown objects." 



I have often thought it a great pity that the new microscopes 

 were not introduced into use by some of those magnificos of 

 science who are, ex officio , the lights of the world, and whose 

 geese are all swans, as, no doubt, they would have taken care 

 that due justice should be done unto them. It is, however, 

 refreshing to hear such an unquestionable authority as Wol* 

 laston assert, that compound microscopes (or engyscopes as 

 I call them) are, by the introduction of achromatic object* 

 glasses, at length capable of making an entertaining exhibition 

 of known objects — (sufficiently perfect, I suppose, to amuse 

 women and children). 



Surely, if a microscope can be proved to possess the power 

 of shewing all the difficult known test objects, both opaque and 

 transparent, it may be safely trusted in an original examination 

 of unknown ones. Where is the object which the best achro* 

 matics, and the Amician reflector (an instrument which the 

 Doctor does not notice, but which is, undoubtedly, capable of 

 greater perfection than the achromatics) do not shew in the 

 most satisfactory manner ? . ^ ■ 



