148 Mr Pritchard on forming Diamonds 



show us a picture of an object instead of nature itself. Now 

 a diamond lens shows us our real object without any sensible 

 aberration like that produced by glass lenses ; and we are en- 

 titled, I think, to expect new discoveries in microscopic science, 

 even at this late period, Jrom very deep single lenses of ada^ 

 mant. * 



* It seems generally admitted that, within a certain range of power, not 

 exceeding that of a lens of l-20th of an inch focus, the beauty and truth 

 of the vision given by the new compound microscopes cannot be equalled 

 by that of any single instrument, at least of glass. It is no less true, how- 

 ever, that the picture of the compound, however perfect, is not like a real 

 object, and will not admit of amplification beyond a certain point with ad- 

 vantage. Under the action of very deep eye-glasses, the image of opaque ob- 

 jects especially, first loses its strong well- determined outline, then grows 

 soft and nebulous, and finally melts away in shadowy confusion. Let the 

 experiment be made of raising the power of a compound up to that of a 

 l-60th inch lens, then try it against the single microscope of that power, 

 (having of course the utmost opening the nature of the object viewed will 

 permit.) The observer, if open to conviction, will soon be taught the 

 superior eflficacy of the latter, for it will show the lines on the dust of Me- 

 nelaus with such force and vivacity that they will always be apparent wilh- 

 out ar\y particular management of the light, nor can their image he extiu' 

 guished by causing the illumination to be di?'ected truly through the axis' of 

 the lens, (as it always may in the compound.) A due consideration of the 

 teeth and inequalities on the surface of a human hair, together with the 

 transverse connecting fibres between the lines on the scales of the Curculio 

 imperialist viewed as opaque objects, will suffice to complete the illustra- 

 tion of the subject ; though the last object is not to be well seen by that 

 kind of light which is given by silver cups, and a single lens of l-60th 

 inch focus can of course have no other. The effectiveness and penetrat- 

 ing faculties of simple magnifiers are invariably increased by an accession 

 of power, however great ; that of compounds seems to be deteriorated be- 

 yond certain limits. An opinion may be hazarded that the achromatics 

 and reflectors yet made do not really surpass the efficacy of equivalent single 

 lenses, even of glass, when their power exceeds that of a l'20th lens ; from 

 l-20th to l-40th, the vision may be about equal, but from l-40th up- 

 wards infinitely inferior. The superior light of the single refraction can 

 reed no comment, and it is evident that there must be a degree of power 

 at which that of the compounds will become too dim and feeble for vision, 

 while that of the single instrument will still retain a due intensity. For 

 these reasons it is conceived, that the close and penetrating scrutiny of len- 

 ses of diamonds of perhaps only the l-200th inch focus, and an equal aper- 

 ture (which their very low aberration would easily admit of,) must enable 

 us to see farther into the arcana of nature than we have been empowered 

 to do. Glass globules of l-200th inch focus, and indeed much deeper. 



