88 



Hough — Mechanical Equivalent of the 



a cup suspended from the arm of a balance to hold the water 

 to be evaporated : (e) two bent levers to balance the friction 

 against gravity : (f\ a recording device to plot the variation of 

 the mechanical force with the number of revolutions : (g) a 

 counter to register the number of revolutions : (h) a clutch for 

 throwing the recorder and the counter in or out of gear at will : 

 (i) a double-walled jacket : (J) a shield between the cup and the 

 jacket to prevent radiation : (k) a steam supply to furnish the 

 steam bath. 



The vertical shaft consists of a hollow steel tube turned and 

 fitted to accurately bored brass boxings. Power is communi- 

 cated to this through the bevel gearing at the top from the 

 horizontal shaft which is driven by a motor. To this horizon- 

 tal shaft is geared, through the clutch by 

 which they are operated, the recorder and 

 the counter. The counter is a Yeeder 

 and gives excellent service. The recorder 

 consists simply of a horizontal drum whose 

 angular velocity is a linear function of that 

 of the brake. This carries the paper verti- 

 cally under the marker. The marker is 

 moved horizontally by means of the famil- 

 iar device for parallel motion invented 

 by Watt. The parts of this registering 

 apparatus are very light and accurately 

 centered on hardened steel cone bearings. 

 They communicate directly with one of 

 the bent levers so that the position of the 

 marker at any instant is a linear function 

 of the mechanical force. The marker is 

 not in continuous contact with the paper, 

 but only for an instant at regular inter- 

 vals when struck by a bar which is actu- 

 ated by a cam geared directly to the 

 drum. The bent levers consist of accu- 

 rately turned cast-iron pulleys with har- 

 dened steel knife edges bearing on har- 

 dened steel surfaces. Attached to these 

 pulleys are pendulum bars and bobs. 

 Flexible steel tapes with swivel joints 

 transmit the moment from the disk of 

 the friction brake to the pulleys of the 

 bent levers. The friction brake consists 

 of a bobbin threaded to the vertical shaft 

 and rotating with it. Two rubbers, 

 quadrant sections of a turned steel tube, 



