DR. GUY ON THE ILLUMINATOR HAND MICROSCOPE. 



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desirous to supply them with some more useful, practical, and 

 ornamental instrument. With this intent, I took with me, at my 

 next- visit, the hand-microscope which Messrs. Powell and Leland 

 had made for me some years since, leaving behind sundry fittings 

 which I need not now describe. I had had good experience of this 

 instrument in my class at King's College, and I now found that, 

 even when restricted to transparent objects, it was equally useful 

 in small social gatherings. Having some experience of the sort 

 of pleasure afforded by the good binocular microscope brought to 

 bear on popular objects, I found the enjoyment far greater when I 

 substituted this hand, or class, microscope for it. The ease with 

 which the objects mounted on the circular disks were changed, and 

 passed from hand to hand, and the unconstrained posture, gave an 

 altogether new character to the entertainment ; and the pleasure 

 afforded was so great that it acted upon me as a strong inducement 

 to find some easy means of dealing with opaque objects. I began 

 my search with a false step. I saw, at first, no better means of 

 throwing light upon the object than the old condenser working in 

 a hole at the end of the instrument. The attempt was a failure, 

 and I became more .desirous than ever of finding some expedient 

 by which my instrument might be restored to that simplicity and 

 readiness of use which I had always looked upon as one of its 

 greatest recommendations when applied to transparent objects. 



I accordingly put myself into communication with Mr. George 

 Smith, foreman to Mr. How, explained the object I wished to 

 accomplish, and the way in which I thought it might be brought 

 about. The result of our consultations and trials was the Illumi- 

 nator^ or Glass Lieherkiilin of which I have been speaking. It is a 

 plano-convex lens, bored with a central aperture, and converted 

 into a concave mirror, by silvering its convex surface. On trial, 

 we found that an opaque object placed in the focus of the rays 

 reflected from this mirror was brilliantly lighted, and clearly seen, 

 in good relief, even in dull dayhght, or the flame of a common 

 candle. 



By this simple expedient, of which the effect much exceeded my 

 expectations, my hand or class microscope was restored to that 

 simplicity, which, as 1 have already stated, was with me one of its 

 chief recommendations. I will not now speak of the improve- 

 ments which may possibly be made in the shape of the Illuminator, 

 nor of certain developments of which the instrument is obviously 



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