SCIENCE IN THE INDUSTRIAL WORLD 



moist with a substance that does not absorb the ink. 

 In this way the antagonistic qualities of grease and 

 water are made to take the place of the raised surfaces 

 in printing. Still another method, practically the same 

 in principle although somewhat different in application, 

 is to blot out on the stone certain portions which are not 

 to appear in the printing, leaving the exposed surfaces 

 for absorbing the ink and transferring it to the paper in 

 the process of printing. These apparently simple proc- 

 esses are subject to endless variations and, of course, 

 require a great number of complicated details in practical 

 lithography. The principle involved, however, is 

 practically the same in all kinds of lithography. 



This method of reproducing pictures was discovered 

 near the beginning of the nineteenth century by Alois 

 Senfelder, a native of Prague. Senfelder, being an 

 ambitious but very poor playwright, had made various 

 experiments in attempting to reproduce pictures for 

 his writings in order to save the expense of wood-en- 

 graving. Having occasion at one time to write some 

 notes, and finding no paper at hand, he wrote these 

 notes upon a slab of stone which he used in grinding his 

 ink. As it happened, the ink used in this writing was of 

 a composition that would resist the action of acid. A 

 few days later, when about to erase this writing from 

 the stone, it occurred to Senfelder to treat the surface 

 with an acid to see what the effect would be. The re- 

 sult was most surprising, for at the end of five minutes 

 the stone had been eaten away to the depth of about 

 one one-hundredth of an inch, leaving the lines of the 

 pen strokes raised in relief sufficiently to receive ink 



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