126 THE MICROSCOPE. 



out the draw-tubes, -whicli will increase the distance between the eye- 

 pieces. 



With this apparatus I obtain the whole of the field of view in 

 each eye; which circumstance I was not prepared to expect, as this 

 must, in some measure, depend upon the correction of the oblique 

 pencUs of the object-glass, for we cannot expect to look obliquely 

 through the objective of a compound achromatic microscope in the 

 same way as in the single lens arrangement, but can only avail our- 

 selves of such oblique pencils of rays as are corrected for passing 

 through the axis of the microscope." 



During the past year Mr. Wenham succeeded in further improving 

 and simplifying this arrangement, a detailed account of which will 

 be found in the volume of the Journcd of Microscopical Sdenoeior 1854. 



APPLICATION OF PHOTOGEAPHY TO THE MIOEOSCOPE. 



When this book was first projected, it was thought that if the ob- 

 jects so beautifully exhibited under the microscope could be drawn by 

 light on the page of the book, or on the wood-block, so that the en- 

 graver might work directly from the drawing thus made, truthfulness 

 would be insured, and we should present to the reader a valuable re- 

 cord of microscopic research never before seen or attempted. But in 

 this we were doomed to disappointment by the existence of a patent, 

 which presented obstacles too great to be surmounted at that time ; 

 and the idea was abandoned, with the exception of a few drawings 

 then prepared, and now ready to hand : the patent restrictions having 

 been since removed, we have embodied them in our pages. The eye 

 and feet of fly, antenna of moth, paddles of whirligig, with a few 

 others, were first taken on a film of collodion, and then floated off 

 the glass to the surface of a block of wood ; the wood having been 

 previously and lightly inked with printer's ink or amber-varnish ; the 

 film was then gently rubbed or smoothed down tO' an even surface, at 

 the same time carefully pressing out bubbles of air or fluid. 



For the purposes of photography the only necessary addition to the 

 ordinary microscope is, that of a dark chamber ; it must indeed form a 

 camera obscura, having at one end an aperture for the insertion of the 

 eye-piece end of the microscopic tube, and at the other a groove for 

 carrying the crown-glass for focussing. This dark chamber should not 

 exceed eighteen inches in length ; for if longei-, the pencil of light trans- 



