[LM111043], Letter from Arthur Edwin Kennelly to New York World, August 20th, 1888


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[LM111043], Letter from Arthur Edwin Kennelly to New York World, August 20th, 1888

Editor's Notes

To the Editor The World"#Dear Sir#having read the article in your issue of last Sunday the 19th entitled "To kill by electricity". I beg that you will allow me to correct a misstatement that has found its way there and also to add a few remarks on the subject.#It is mentioned that Experiments in killing dogs under the supervision of so able an electrician as Thomas A. Edison resulted in the hides of some of the animals being split open"--. Having carried out those experiments under Mr Edison's instruction for the purpose ascertaining by exact measurement the amount of electricity which requires to be passed through a dog in order to kill it. I am in a position to say that in no case has the hide been so split.#These have been only two cases in which the skin of the animal has suffered any damage and that was as burning or charring effect produced in our first trials before we had learned the best method of passing the current through the body. It may be mentioned that it can always be arranged to kill or dog instantly by electricity without any external sign left on the animal showing how death was inflicted, and without sign mean or struggle. The animal falls motionless.#In all cases where persons hav been burned by accidentally coming in contact with electric light wires, the burning is traceable to the insufficient contact that has existed between the wire and the person of the sufferer had the contact been more perfect that is to say had it taken place over a larger and wetter surface of skin there can be no question that the burning would not have resulted, although it is probable that the shock would have thereby been more disastrous in its effect on vitality.#While it must be admitted that the amount of current that will kill a dog is perhaps considerably less than that which is necessary to kill a human being, and also that [two lines crossed out] both human beings and dogs differ very much among themselves in their susceptibility to injury by electricity, still there are in the absence of direct measurement on human beings, limits of proposition within which our conclusions may be trusted.#The results of experiments made at Mr Edison's laboratory point to four conclusions.#1st That in the case of continuous currents or those which flow continuously in the same direction the fatality of the current depends upon its strength and also to some extent upon the time of application. For example a current of one forth of an ampere might be fatal during in application of twenty seconds though not fatal during five. The fatality though it thus increases with the time does not seem to do so in anything like direct proportion-- 2nd That with alternating currents on those that vary rapidly in direction to and fro, the fatality of the current depends upon its strength, the time of its application, and also upon the number of alternations per second or rapidity of reveresal. The effect in this case seems to be more nearly proportional to the time of application or the number of alternation than is to be observed with the continuous current. 3rd That the rapidly alternating current is under otherwise similar conditions beyond all doubt more fatal than the continuous current. The exact difference cannot be stated accurately owing to the great range of vitality and susceptibility that different dogs evince, but it would appear on an average that the former in two and a half or three times more fatal than the latter, under the same set of conditions. 4th That the effect of the current when passed between one fore leg and one hindleg is chiefly on the nervous system and not so much on the heart or its only nervous centre. As a rule the heart of a dog killed by the current beats for some time after unconsciousness and death have reached the brain. In one cell examined by Dr Peterson the heart beat for more than thirty minutes after death had been produced.#There seems to be no good ground for the opinion that the resistance of an animal or its variation has any direct bearing upon its vitality or its susceptibility to electrical injury. The matter is generally misunderstood. The resistance of a price of homogenous metal is a definite quantity depending upon its shape and nature, but the resistance of a human being is not capable of similar definite statement. First of all he is composed of heterogenous material largely fluid, and essentially of variable resistance, and secondly he is encased in dead matter, superficialy covered with horny epidermis a very bad conductor. If the hands are dry and each grasps a wire the resistance between them may be very large. It would therefore require under those circumstances a large electrical pressure to force a fatal current through him. But when the skin is moistened by perspiration or wet applications, and the surface of contact with the conductors conveying the electricity are sufficiently enlarged, the resistance of the body can be reduced almost to any limit. So that when the resistance of a human being or any animal is stated to be so many ohms the statement simply defines the particular resistance of the animal's body and skin, under the existing conditions of area, moisture and pressure of contact, and that the variation of any of these letter would change the resistance perhaps many time. The fact is generally noticed that the measured resistance of a dog talks when a strong current is passed through his body. That means that either the electricity in traversing his tissue has altered them more favorably to conduction or what is quite as likely that the contact at the surface of the skin has in some way been improved#The electrical pressure which will kill a dog within thirty seconds, seems to vary for the particular method of contact employed in the Edison Laboratory experiments according to the size of nature of the animal between 300 and 700 volts for continuous and between 100 and 250 volts for alternating currents. The pressure which is required to kill instantly day within two seconds is greater and may be roughly taken as three times those amount.#How much more than this current is required to kill a man we do ont at present know but it is probable that sustained electrical pressure of three thousand volts alternating say 500 times per second through good contacts made perhaps by bandages on the wrists moistened with salt water, the contact being even more important than the voltage, will suffice for the purpose of criminal execution. These will be at least under those circumstances no mutilation, and death if not instantaneous would be a question of seconds. Yours faithfully A.E. Kennelly Electrician Edison Laboratory. [Anot with D8855ABL 880821]





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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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