Oil some Modifications of Recording Ajjparatus. 347 



When the clock starts runniug, the speed increases, the plates 

 tend to separate, and offer an increased resistance to the air. 



Two different speeds can be obtained by means of an 

 interchangeable gearing between the fourth and fifth wheels of 

 the train. By moving a check on the lower clock plate, the 

 arbor of the fourth wheel can be shifted so as to bring a pair 

 of wheels of different diameters into gearing, and thus the 

 speed is increased four times. The arbor of the second wheel 

 is carried 1 in. through the upper plate, and is brought to a 

 quick point. On this fits tightly a circular brass disc 1| in. 

 in diameter, in such a way as to have the pointed end of the 

 arbor projecting -|- in. This disc has two stout steel pins 

 f in. in length, screwed into its upper surface near its margin, 

 and separated from each other by ^ in. The spring is 

 wound from the end opposite the regulator, by means of a 

 key acting on it by a pair of bevelled wheels. 



The clock rests on three legs, one under the regulator, and 

 a pair at the opposite end. These latter are continued up- 

 wards into two uprights, 3| in. apart at the base, and li in. 

 at the top, where they are connected by a stout crosspiece. 

 Two cross bars at the lower part of these give a firm con- 

 nection to the clockwork by means of strong screw^s. On the 

 piece joining the top of the uprights, a thick arm of brass pro- 

 jects 3 in. over the clockwork, and receives at its further end 

 a pointed steel screw with milled head and running washer. 

 The point of this screw is exactly over the pointed end of 

 the arbor of the second wheel, which carries the brass disc 

 referred to above. The drum is 6 in. in diameter, and 5J in. 

 deep, and is similar in construction to the drums ordinarily 

 employed. It is provided with a collar and clamping screw 

 at the top, so that it can be fixed at any point on the spindle 

 which carries it. 



This spindle is a w^ell-turned steel rod 8 in. in length, 

 and yV in. thick. It is cupped out at each end, so as to 

 receive the bearing points already described. It is further 

 pierced by a hole I in. from the lower end. When in 

 position on the clock, a pin passes through this hole and 

 between the upright steel pins on the disc. Thus, when the 

 clock is started, the spindle is carried round with the disc. 



