6 



On the " Autographic " Process of Lithography as 

 applicable to the illustration of scientific papers. 



By Arthur Cottam, F.R.A.S. 

 {Bead December 28th, 1877.) 



It will, I doubt not, be readily admitted that the value of many 

 a scientific paper is greatly increased by good illustrative plates. 

 Many papers would be almost unintelligible unless illustrated. And 

 again the value of the illustrations is very much greater when they 

 are drawn by the author of the paper they are intended to illustrate. 

 To have plates drawn by a professional draughtsman is always ex- 

 jDensive work, and unless the draughtsman has some knowledge of 

 the objects to be figured, it is a matter of no little difficulty — some- 

 times almost an impossibility — to explain to him the special features 

 that are to be brought out, and the minute differences and gradations 

 of light and shade upon which the value of a drawing frequently 

 depends. 



A process that will enable any one who can draw fairly well — and 

 I suppose all microscopists can draw more or less, at all events they 

 should be able to do so — to draw his own figures, and to have them 

 printed in facsimile in any numbers, and at a very small cost, is a 

 process so likely to be valuable to the members of this Club, that I 

 am anxious to introduce the new " Autographic " process to you, 

 as I believe it will be found to possess all these advantages. 



To explain it, I must briefly describe the ordinary processes of 

 lithography. 



Drawings on stone are made with a greasy ink, manufactured on 

 purpose, or with lithographic chalk, which is also greasy. The 

 stone, which is very porous, absorbs the grease wherever it is laid 

 upon it. When the drawing is complete, the stone is washed over 

 with gum-water, which soaks into the stone wherever there is no 

 greasy ink or crayon. When the gum is dry, a roller of printing 

 ink is passed over the stone, and the ink adheres to the greasy parts 

 but will not touch the gummed surface, and by renewing the ink any 

 number of impressions can be printed off. 



