Royal Microsco'pical Society. 73 



III. — On a SimjyJe Method of Preparing Ledure-IlJustraiions of 

 Microscopic Objects. By Kev. W. H. Dallinger, F.R.M.S. 



(Bead before the Eotal Microscopical Society, Jan. 7, 1874.) 



Most working microscopists have felt the necessity, in reading 

 papers on their work, of accurate illustration. Mere 'enlarged 

 drawings fail in matters of detail, unless extravagant labour is 

 expended, and considerable skill employed. Even then, the hght 

 of an ordinary lecture-hall is not enough to enable the most distant 

 of the audience to clearly see them. It is only by means of the 

 lime-light and transparencies that really useful illustrations can be 

 given. But, here, the difficulty is to prepare them accurately and 

 inexpensively. Photography cannot be employed in all cases ; and 

 even where it can be, it involves more labour than most working 

 microscopists can afford for every paper they may read. DraA^-ing 

 and painting on glass in the usual method is an art that it takes 

 years thoroughly to learn ; and to employ one who has learned it 

 to draw from nature a highly magnified object, would be to intro- 

 duce unnumbered errors of interpretation, unless our artist be a 

 microscopist himself. 



I obviate all these difficulties by the following method : — 

 On finely-ground glass, drawing with a blacklead pencil is as 

 easy as drawing on London board. I get 4-inch squares of glass 

 to suit my lantern, carefully ground on one side hke the focussing 

 glass of a camera. Now with the ground side up the camera lucida 

 may be used with this as well as with drawing board if a piece of 

 white paper be placed beneath it, and the object drawn in the usual 

 way. For outlining and delicate shading I employ H H H H and 

 H H H pencils ; for deep shadows I use H B. By a very dehcate 

 employment of the pencil, shadows softer than can be secured by 

 lithography may be made. The camera lucida, of course, is not 

 necessary ; we may draw with the eye and hand alone. If it be 

 necessary to put in colour, it may be done, cleanly and carefully, 

 over the shading ; thus, one layer of colour suffices. Now, of 

 course, although we have a perfect drawing of the object, with all 

 the detail accurately given, it is not a transparency. But we can 

 easily make it one. Thin some good pale Canada balsam with 

 benzine to about the consistency of cream ; and simply float it over 

 the ground surface of your glass ; pour off till the drop comes very 

 sluggishly, then reverse the glass so that the corner from which the 

 balsam was flowing off be placed upward. Let the return flow reach 

 about the middle ; then reverse it again, and move it in several 

 directions to get the balsam level. This may be done with a very 

 Httle practice so that the surface shall be undistinguishable from 

 glass. We have now a perfect transparency. AU that is required 



