DRA wixa ] 63 



Drawings for Zinc Etching. -The zinc (or coppci) 

 etching used in the reproduction of hue drawings reproduces 

 faithfully all the methods used in the old wood cuts, such 

 as fine dotted shadings, dotted lines, fine parallel line 

 shadings, or cross-hatchings. Hence there appears no 

 need, as a rule, to use the (sometimes blurred) half-tones 

 for the reproduction of microscopical drawings, and these 

 can perhaps be reserved for photographs. In drawings, 

 the reference letters or numerals should be small and as 

 light as possible, so as not to be conspicuous to the detriment 

 of the drawing. The writer dots them in, whenever 

 allowable. 



Drawings for Lantern Slides. — If lantern shdes of chro- 

 mosomes are required, the following method gives excellent 

 results, and is also available for half-tones, if they are 

 wanted. Draw the chromosomes, etc. in solid black on 

 Bristol board with Higgins' waterproof india ink. When 

 quite dry, apply an ordinary red rubber pencil eraser for a 

 sufficient time to each chromosome to lower it to a half-tone. 

 Any specially interesting chromosome to which attention 

 is to be called can be left black. 



Other Methods. — Drawings for half-tone reproduction 

 are said to be best done with a brush and sepia (or the 

 water color can be used in an ordinary pen). 



Line drawings of microscopical objects can also be made 

 by taking a photograph through the microscope, and 

 making a light print; after enlarging, if necessary. This 

 print is then made the basis for a line drawing in waterproof 

 india ink. When quite dry, this is dipped into dilute solu- 

 tion of iodine, until all the silver is turned into yellow iodide. 

 Then it is put for a short time into hyposulphite solution, 

 which dissolves the iodide; and it is finally washed. 



Microscopical drawings are readily enlarged by projecting 

 a lantern shde made from them on to the drawing paper. 



Colored Drawings. — If colored drawings are needed, 

 the use of certain typewriter "second " paper, which absorbs 

 the colors, is good. The colors indeed cannot be readily 

 washed out on this paper if a false stroke of the brush is 



