APPLICATION OF PHOTOGRAPHY. 155 



A fine effect may be obtained by using Furze's spotted 

 lens, with a Herapathite polariser; see Mic. Soc. Trans. 

 2d series, vol. iii. p. 63. 



APPLICATION OF PHOTOGRAPHY TO THE MICROSCOPE. 



At the time this book was projected, it was thought that 

 if the objects so beautifully exhibited under the microscope 

 could be drawn by light on the page of the book, or on 

 the wood-blocks, so that the engraver might work directly 

 from the drawings thus made, truthfulness would be in- 

 sured, and we should present to the reader a valuable 

 record of microscopic research never before seen or 

 attempted. But in this we were doomed to disappoint- 

 ment by the existence of a patent, which presented ob- 

 stacles too great to be surmounted ; and the idea was 

 abandoned, with the exception of a few drawings then 

 prepared, and 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 whirli- 

 gig, with a few others, were first taken on a film of collo- 

 dion, then floated off the glass on to the surface of a block 

 of wood, the wood having been previously and lightly 

 inked with printer's ink or amber-varnish, and the film 

 gently rubbed or smoothed down to an even surface, at 

 the same time carefully pressing out all 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 should 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 

 must not exceed eighteen inches in length ; for if longer, 

 the pencil of light transmitted by the object-glass is dif- 

 fused over too large a surface, and a faint and unsatis- 

 factory picture results therefrom. Another advantage is, 

 that pictures at this distance are in size very nearly equal 

 to the object seen in the microscope. In some instances, 

 Detter pictures are produced by taking away the eye-piece 



