88 Mr. C. Y. Boys on Apparatus for the 



while the frame carrying the racks can move either longi- 

 tudinally or laterally. A pin projecting centrally from the 

 pinion enters the slot, which is shaded in the figure, and so 

 causes the pinion to gear with the two racks alternately. This 

 lateral movement of the rack-frame is made use of to depress 

 the integrating-cylinder during its back stroke, at which time 

 the magnet rests on the shoulder S. As the tangent of the 

 inclination of the tangent-wheel is proportional to the current- 

 strength, and as the rate of rotation of the cylinder is propor- 

 tional to the tangent of the inclination of the tangent-wheel, 

 the cylinder will turn with a speed which is proportional to 

 the current-strength, and the whole number of turns, as shown 

 by the counter, will be a measure of the quantity of electricity 

 that has passed. In the arrangement described, time is divided 

 into a great number of equal intervals, and the current-strength 

 during each alternate one considered. After any consider- 

 able time, such a sampling of the current would give just 

 as exact a result as would be obtained by integrating continu- 

 ously. A quick-return mangle-motion might be employed to 

 diminish the proportion of ineffective time; or the whole time 

 could be made effective by keeping the cylinder in continuous 

 contact, and actuating a reversing-gear between the cylinder 

 and a counter by means of the lateral movement of the mangle- 

 motion. It would be well to employ a catch on the armature 

 of a subsidiary electromagnet, so as to stop the clockwork, 

 except when a current is passing. This current-meter, like 

 Edison's electrolytic meter, is a direction-meter. If the cur- 

 rent is passing in one direction, it counts it positive ; if in 

 the opposite direction, it counts it negative. A reverser actu- 

 ated by a polarized armature could be employed to make the 

 meter count as positive, a current passing either way, and so 

 make it applicable to the case of alternating currents. An- 

 other kind of current-meter, which is by its nature indepen- 

 dent of the direction of the current, would be preferable to the 

 magnetic-needle meter and reverser combined. 



Figs. 11 and 12 represent an electric-energy meter, which 

 will be described later ; but they will serve as diagrams to 

 illustrate a description of the second current-meter, m m is 

 the mangle-motion, which causes the cylinder C to reciprocate 

 and bear alternately against the two tangent-wheels 1 1. 

 These wheels are mounted in a common swivelling-frame, 

 which ordinarily is kept vertical by the weights X X, but 

 which may be inclined by a force due to any cause tending to 

 turn the beam B. Now the turning-power of the weights 

 XX varies as the sine of the inclination ; while the turning- 

 power of a force acting downwards applied to the point p varies 



