Machine for producing High Tension Electricity. 177 



secondary wire is effected with much less length of wire. In other 

 words, a given weight of material utilised in a number of small coils 

 ought to yield a greater output of energy than the same weight used 

 in the construction of one large coil, the best proportions of length to 

 diameter being in each case adhered to. Moreover, it is well known 

 that, with induction coils of exceptional magnitude, the ordinary 

 vibrating contact breaker cannot be efficiently employed on account 

 of the rapid destruction of the platinum points; and the method of 

 obviating this difficulty by breaking contact under a cover of alcohol 

 is only compatible with slow action. But by dividing the work 

 amongst several coils, each with a separate vibrating contact breaker, 

 this difficulty is avoided, and the frequency of the spark is multiplied 

 in proportion to the number of coils and contact breakers. With 

 these views, I obtained from Mr. Apps six induction coils, each 

 capable of yielding a maximum spark of 10 inches. I had also a 

 six-fold contact breaker constructed of the usual automatic vibrating 

 type, and in which each vibrator was acted upon by an independent 

 electro-magnet of the horse-shoe description. In experimenting with 

 a single contact breaker used with a single coil, I found much 

 advantage in augmenting the power of the working magnet, and in 

 stiffening and shortening the spring greatly beyond the limits <f 

 ordinary practice. By so doing I was enabled to reduce the range of 

 vibration, and thus to obtain with a heavy-headed vibrator many times 

 the usual speed of oscillation without reducing the length of spark in 

 nearly the same proportion. With an extremely high speed of inter- 

 ruption, I could obtain sparks 4 inches long in great profusion, 

 though not with rapidity equal to the rate of vibration. To accom- 

 plish that degree of rapidity the sparking distance had to be reduced 

 to about one-half; but, considering that a spark of 2 inches is sup- 

 posed to represent nearly 95,000 volts when delivered between knobs, 

 and would probably give two-thirds of that amount when delivered 

 between points, I saw no sufficient inducement to strive after longer 

 sparks, which can only be obtained by great sacrifice of frequency, 

 involving a general reduction of amperage far exceeding the gain 

 in voltage. 



By using two coils in series with an alcohol contact breaker worked 

 slowly, I could get sparks 15 inches long ; but I found so many diffi- 

 culties and inconveniences in a serial arrangement, and so little to be 

 gained by it, that I abandoned the pursuit of it, and confined my 

 attention to a combination in parallel. In the first instance I em- 

 ployed a secondary battery of seven large cells to supply the current 

 for exciting my six coils, and I fully expected that their united 

 output would be proportionate to their number, but in this I was 

 disappointed. I found that two coils gave me only about one and 

 a-half the effect of one, and that every additional coil gave a dimin- 



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