METHODS OF RESEARCH: DRAWINGS 127 



seen an object to much profit if he cannot make at least a 

 sketch of it, and this, however rude, is better than nothing, and 

 helps just that much toward his intellectual development, 

 which, after all, is the end of most of his studies. 



Drawings may be made with lead pencil, pen and ink, or 

 the brush. 



Pencil drawings well made, are very attractive, and if there 

 is not a question of expense they may be used to illustrate 

 scientific papers by means of lithography, but this process is 

 much more expensive than line engraving (zinc process) or 

 half-tone plates, and is now seldom used by publishers except 

 for expensive works. Drawings designed to illustrate books 

 and papers should, therefore, be made, as a rule, with India ink, 

 by use of pen or brush. The latter, known as wash-drawings, 

 can only be half-toned. The former are generally reproduced 

 by the zinc process. Zinc cuts are less expensive than the cop- 

 per half-tones, print well, and are very attractive if well made. 

 To get good results the ink must be black and non-soluble in water, 

 the lines or dots must be distinct in all parts and must be prop- 

 erly spaced, so that when the drawing is reduced, none of them 

 will fade out in places, owing to insufficient or pale ink, or run 

 together into blotches because not properly spaced. The 

 student should have a clear idea in advance of where he intends to 

 introduce his lights and shades so as to produce an attractive 

 picture, and how any part will appear when it is reduced one-half 

 or two-thirds. For this reason he should examine his drawing 

 from time to time under a reducing glass, and when it is done 

 not allow it to be reduced more than it will stand. I recall 

 seeing many years ago a hundred beautiful pen-and-ink drawings 

 made by one scientific man for the use of another. They were 

 drawn and marked to be reduced, according to my recollection, 

 just one-half and would have stood that amount of reduction 

 perfectly, but for reasons of economy they were reduced twice 

 the proper amount with disagreeable blotchy results, satisfactory 

 neither to the artist nor to the author. Whenever in doubt 

 the finished drawing should be photographed at the proposed 

 reduction. This is a sure way of deciding how much re- 

 duction any drawing will stand. A finished drawing represents 



