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HISTORY AND PROGRESS. 59 



outside the circumference swept over by r ; so that if the 

 latter make another revolution whilst the finger is kept 

 down upon the key, no second contact is made, and the 

 same letter is not repeated. The operator feels a vibration 

 of the key as the shovel passes by the pin, and is thus made 

 aware that the letter has been printed. 



The type-wheel H contains on its circumference, in twenty- 

 eight equal spaces, twenty-six letters of the alphabet, a dot, and 

 a blank space ; it is fixed to the extremity of the axis cc, which 

 is put in motion by means of the hollow axis G, enveloping 

 it in the greater part of its length. The connection between 

 c c' and G is made by the mediation of a fine rachet- wheel, 

 G 5 , attached to the axis G, the click m l being on the axis c c'. 

 On the latter are supported, besides the type-wheel and click, 

 a corrector, H', or wheel with long narrow teeth, equal in 

 number to the types, serving to establish precision between 

 the movements of the horizontal arm r and the type- wheel. 

 On the same axis is a wheel, HJ, having a notch at one part 

 of its circumference for stopping the type-wheel when the 

 blank space is opposite the printing press, in case it should 

 spring forward. 



The hollow axis G is turned by a clockwork moved by a 

 weight, a wheel of which engages with the pinion G X , and 

 supports, besides the racket G 5 and bevilled- wheel G 2 already 

 mentioned, the escape wheel G 4 and a tooth wheel G 3 , which 

 locks into the pinion ij (Fig. 30) of the printing shaft I. 



The printing shaft turns seven times as fast as the type- 

 wheel, and carries a fly-wheel, i", at one extremity, in order 

 to overcome the inertia of a small shaft, whose duty is to lift 

 the paper up to the type-wheel at the other extremity. This 

 is shown partly in section in Fig. 30. The printing shaft i 

 and its continuation i are locked together by means of a 

 ratchet-wheel, i lf and click, i'. At the end of the continuation 

 shaft i is a cam, h lt for lifting the press and the paper against 

 the type- wheel. 



The printing press is shown in Fig. 29. Underneath the 

 type-wheel is a small cylinder a, over which the paper is led, 

 its axis being in the middle of a bent lever, b, turning at a ; 



