194 Miscellaneous Intelligence, 



microscope, to co-operate in forming the image, but which is here 

 used only as an illuminator, being removed beyond the focus of the 

 concave metal. 



Any Amician instrument may, of course, be easily modified into 

 this form, for it will be merely necessary to draw its plane metal 

 further back, and to perforate a fresh hole in the side of the tube to 

 admit the light, with some additional contrivance to present the 

 object in its proper place. This reflector, considered only with 

 reference to its optical principle and performance, is at once the 

 most simple and the most perfect of the whole family of compound 

 microscopes, but has nearly the same inconveniences as the other, 

 relative to the application of objects. To those who regard not the 

 difficulty at which they procure perfect vision, this instrument must 

 be highly valuable, and probably will long retain a place among 

 microscopes as a verificaior or proof engiscope ; for there can be no 

 doubt that the vision it affords is of the purest and most un- 

 adulterated nature. 



2. Carpenter*s Aplanatic Solar Microscope. — This is the first 

 solar instrument which has ever possessed achromatic object-glasses 

 regularly worked to correct diverging rays. The experiment of 

 converting telescopic object-glasses of short foci to the purpose of 

 forming an image for the solar microscope has been oflen made, 

 but of course without any good effect ; it is as rational to expect 

 that such glasses should answer both for divergent and parallel 

 light, as that the same medicine should cure a diabetes and a 

 dropsy. The pictures of microscopic objects given by the present 

 instrument are totally freed both from chromatic and spherical aberra- 

 tion, and in consequence of which the coloured fringe which forms 

 the outline of all objects shown with common object glasses is re- 

 moved, together with that nebulous indistinctness which causes the 

 image to appear a mere shadow when inspected closely, and, there- 

 fore, fit to be viewed only from afar. 



The observer may boldly proceed up to the very screen on which 

 the picture is formed by the achromatic glasses, and will find that 

 the image instead of losing by this close scrutiny developes those 

 minute details which were invisible at a distance. But it is chiefly 

 when opaque objects are viewed that the incontestable superiority 

 of the achromatic shines forth in all its splendour (especially if con- 

 trasted with the effects of common glasses, which, it is well known, 

 give an image of radiant bodies, which is a mere jumble of aberra- 

 tion of both kinds, not fit for public exhibition.) 



Those who fancy that aplanatic glasses are no better adapted to 

 the nature of a solar microscope than to that of a camera-obscura, 

 would do well to examine Mr. C.'s instrument ; in fact the public 

 voice has already decided the question, 



The frame of this instrument is on a gigantic scale, the illuminat- 

 ing lens being a foot in diameter, with everything else in proportion. 



