104 SEC. 3. MEASUREMENT. 



indicated will be read off a dial. As a peculiarity it may be mentioned that 

 the scale of the dial shows a uniform division, although the position of 

 the balancing balls moving the pointing hand depends according to a 

 complicated law on the velocity of the rotation of the spindle. 



The motion is worked by means of straps and pulley, and can, as a matter 

 of course (on vessels, &c.), be effected by a fixed connexion with a shaft- 

 movement. 



The winch-handle, however, will enable the spectator to put the instrument 

 in motion by the hand. 



The accuracy of the indications of the instrument will be augmented if the 

 pointing hand is turned off a little with the finger in the direction of the pro- 

 gressive numbers, and then allows it to jerk back freely. 



A forcible turning of the pointing hand in the opposite direction, toward O, 

 is not allowed. 



41 5a. Revolution Indicator, to show the rate at which 

 machinery is working. Frederick Guthrie. 



From the machinery an up-and-down motion is communicated to the piston 

 of a pneumatic forcing pump. The compressed air escapes through a fine 

 opening, and also exercises pressure on oil, water, or mercury, in a vessel 

 provided with a manometer tube. The height of the liquid in the tube 

 measures the rate at which the pump and machinery are working. 



488 d. Drawings of a Simple Counter, and of a Registering 

 Counter. 



(Sec Report of Baron Seguier to the Society of Encouragement, 

 1844.) M. Winnerel, Paris. 



VII. MEASUREMENT OF MOMENTUM. 



417. Model of the Ballistic Pendulum, erected in the 

 Royal Arsenal in 1814, and transferred to the Royal Military 

 Repository in 1836. Weight, 7,740 Ibs. Centre of gravity below 

 centre of suspension 10'97 ft.; centre of oscillation below centre 

 of suspension 1 1 88 ft. Scale Jth. Major M. L. Taylor, R.A. 



418. Navez Electro-Ballistic Apparatus. 



Major M. L. Taylor, R.A. 



41 8a. Discussion on Electro-Ballistic Apparatus. 



419. Model of Ballistic and Gun Pendulum, as erected 

 at Shoeburyness in 1858. Oscillating system of gun pendulum, 

 weighs 37 Ibs. 10-5 oz. ; that of the block pendulum weighs 

 31 Ibs. 8-25 oz. Scale, Jth. Major M. L. Taylor, R.A. 



VIII. MEASUREMENT OF FORCE. 

 42 la. Attraction Meter. An instrument for measuring 

 horizontal attraction. j) Tt Siemens. 



