The first execution of a criminal by electricity was performed in Sing Sing Prison, New York State, in 1890. There was at that time a hot controversy among experts over the question whether death, or merely unconsciousness, could be produced by electricity. To be on the safe side the legislature passed a law requiring that the electrocution of a criminal should be followed immediately by the dissection of his body. Only six states out of forty-nine have thus far adopted that method of capital punishment, five have abolished capital punishment, and thirty-eight still prefer hanging to electrocution. But it should be remembered that it is amperes, not volts, that kill. One often hears the meaningless expression, "he received 2000 volts into his body." The volts indicate the pressure, analogous to pounds per square inch of water pressure. Amperes of electricity are analogous to gallons of water. It is possible to have exceedingly high voltage of electricity without amperes enough to do damage. When one holds his finger near to a rapidly moving leather belt and a stream of sparks passes between the finger and the belt, the voltage may be 50,000 or even 100,000, but the quantity in amperes is too small to do any damage or even produce much sensation. A similar thing is true when one produces sparks by rubbing a cat's back, or lights the gas by a spark produced by rubbing the feet upon a carpet. Such sparks are miniature lightning discharges. The real lightning does damage because it furnishes quantity, measurable in amperes, as well as extremely high volts of pressure.
At this point I was reminded by the boy who had received a shock from the engine that morning that he had touched only one binding post. How then had he closed a circuit through his body, and how could he receive such a terrible shock when there were only a few battery cells to produce the electric current. I replied that he had the distinction of having encountered about a 5000-volt current. In the language of the newspapers he might say, Took 5000 volts and still live. We must next proceed to show how he really did close the circuit and how the spark coil enables a battery of a few dry cells to produce exceedingly high voltages.
XI
THE ELECTRICAL SPARKING EQUIPMENT FOR A GASOLENE ENGINE
Under the shade of a great sugar maple, with Millville Lake spread before us, we took apart and examined the entire equipment for producing the electric sparks to explode the mixture of gasolene and air in the cylinders of our motor boat. The engine has two cylinders. For each cylinder there is a separate battery and spark coil. Inasmuch as the electrical outfit is duplicated for each cylinder it will be necessary for us to consider the case of one cylinder only.
When this engine is running, 700 explosions per minute are produced in each cylinder. In one-twelfth of a second the following four events take place:
1. The cylinder is swept clear of the products of combustion formed by the last explosion.
2. Four drops of gasolene are vaporized and mixed with one quart of air and pushed into the cylinder by the pressure of the atmosphere.