THE PRINTING PRESS. 



slab, aids materially in diffusing the ink in a perfectly uniform 

 stratum. 



An illustrative diagram of a double printing-machine is shown in fig. 6, 

 where and D' are the two paper-cylinders ; A and A', the two forms ;, 

 i i i and i' i' i', the inking-rollers ; c c and c' c, the diffusing-rollers ; and 

 c and c' the ductor-rollers. The pile of paper placed on the table E, is 



Fig. 6. 



supplied sheet by sheet to the tapes between which it is held ; and being 

 passed over the roller R, and under the cylinder D', it receives the impres- 

 sion of the types of the form A' ; it then passes successively over the roller 

 T', under T, and round the cylinder D, at the lower point of which its 

 imprinted side comes into contact with the types of the form A, by which 

 it is printed ; after which, the tapes opening, it is thrown out by the cen- 

 trifugal force upon the receiving table p. 



It will be apparent by the figure, that while the sheet is printed on one 

 side by the form A', the form A is passing between the inking-rollers i i /, 

 and the slab B ; and on the contrary, while the paper is printed on the other 

 side by the form A, the form A' is passing between the inking-rollers i' i' i' 

 and the slab B'. 



In this manner, by each alternate motion from right to left, and 

 from left to right, a sheet is printed on both sides. 



22. A perspective view of a double-acting printing machine, as 

 constructed by Messrs. Applegath and Cowper, is shown in fig. 7. 



A boy, called the layer-on, E, standing at an elevated desk, 

 pushes the paper, sheet by sheet, towards the tapes, which, closing 

 upon it, carry it over a roller R, passing under which it is carried 

 to the right of the cylinder D, under which it passes, and being 

 carried up to the left of it, passes successively aver the roller T, 

 under the roller T', over the cylinder D, and drawn along its left 

 side, after which it passes under it, and is flung into the hands of 

 a boy, F, called the taker-off, seated before a table placed between 

 the two cylinders D and D', upon which he disposes the sheets as 

 he receives them. 



In this manner the layer-on feeds the machine in constant 

 succession with blank sheets, which, being carried under the 

 cylinder D, are printed on one side, and afterwards under the 

 cylinder D', are printed on the other, when they are received by 

 the taker-off. 

 14 



