ETCHING ON GLASS. 445 



where the varnish was appUed will continue trans- 

 parent and seem extremely bright. It is to be 

 noticed, when the liquid fluoric acid is used, the 

 lines which have been etched continue still trans- 

 parent ; but when the gas has been employed, the 

 line is white and opaque, as if cut by a wheel. 



LITHOGRAPHY. 



This art is so called, because the impressions 

 are produced from drawings made on stone. It 

 was invented by Aloys Sennefelder, a German, 

 about the year 1800. 



There are several styles of drawing employed in 

 lithographic prints. The chief are, the line manner, 

 and the chalk manner. In the line manner, which 

 is similar in its effect to the line engraving on cop- 

 per of second rate quality, lines are drawn on a 

 stone with a particular sort of ink, by means of 

 pens of various kinds, or a camels-hair pencil. 



In both these methods, the same kind of stone is 

 used ; but in the line manner, the stone must be 

 polished smooth with pumice-stone, whereas, for 

 the chalk it is made a little rough, by grinding with 

 sand. The stone must be calcareous and of a light 

 colour. The white lias in this country answers 

 tolerably well, but is not so fit as the German 

 stones. 



The lithographic ink is composed of equal parts 

 of tallow, bees-wax, shell lac, and common soap, 

 with a sufficient quantity of lamp-black to colour 

 it. These ingredients are mixed by heating them. 



