184 
The Newly -Discovered Force . 
[April, 
through a large vessel filled with water, and pieces of iron 
and bars of iron of various sizes were placed across its track 
and rested upon the wire, and the wire was wound round an 
iron press, and yet at the end the spark appeared. Mr. 
Edison took the wire out of doors, ran it along the ground 
and in a ditch on a rainy night, and brought it up-stairs 
several rods from the battery, and the spark was seen by 
him, by his assistant, and by myself in the dark box above 
described, but it was not constant, and required a nice 
adjustment of the carbon points to bring it out. The force, 
therefore, does not readily leave the metallic conductor, even 
when in contaCt with the earth or passing through water, 
and the spark is seen when the end of the wire conducting 
the force is at a long distance from the battery. 
Physiological Effects . 
1. The force is conducted by the human body. This was 
proved by taking hold of the conductor — a wire, iron bar, or 
gas-pipe — that was in connection with the apparatus, 
evolving the force by one hand, and with the other touching 
the blade of a knife to a stove or block of metal : sparks 
appeared, though somewhat smaller than when the force did 
not traverse the body. In some of these experiments, 
which were tried on several individuals, the body was insu- 
lated by a large block of paraffin 6 inches thick. When the 
distance for the force to travel through the body was 
reduced one-half — by making the connection at the back of 
the neck or in the mouth — a somewhat larger spark was 
produced than when the whole resistance of the body from 
hand to hand was included. It was clear, therefore, that 
the body conducted the force, though not so well as 
metals. A person standing on an insulator, with the con- 
ductor in hand, does not, on dropping the conductor, give 
any evidence of being charged ; he can give no sparks to any 
other person or to any metal. I have also found it impos- 
sible to charge metals. 
2. The force in passing through the body produces no 
demonstrable physiological effects. While we have the 
evidence of the sparks that the force is traversing the body, 
yet, wherever directed, it causes no sensation, not even on 
the tip of the tongue, no muscular contraction anywhere, 
no tremor, no erection of the hair, no flashes of light, no sour 
taste, no dizziness — in short, none of the usual physiological 
reactions of the different forms of electricity. Mr. Edison 
had supposed that in his own case contraction of the muscles 
