Anyone who has had the opportunity to charge small children to thousands of volts will appreciate the skill and showmanship of the dangling boy demonstration.
Stephen Gray became a victim of Newton’s vengeful behaviour following an argument over data. At Greenwich Observatory, the Astronomer Royal, John Flamsteed, was producing the eighteenth century’s most meticulous star catalogue. It was his life’s work. He was a careful, thorough man, aware that his reputation depended on the accuracy of his charts.
Newton needed the data and Flamsteed reluctantly agreed to let him see it. But Newton published the data without Flamsteed’s knowledge or permission. Newton was unapologetic. Flamsteed was furious:
I had resolved aforehand his knavish talk should not move me… I complained then of my catalogue being printed by Raymer, without my knowledge, and that I was robbed of the fruit of my labours. At this he fired, and called me all the ill names, puppy, etc., that he could think of.
Letter from Flamsteed to Abraham Sharpe printed in ‘The Royal Observatory Greenwich’
The two men were never reconciled. Newton was not a man to build bridges. This was unfortunate for Stephen Gray. Flamsteed was Gray’s great supporter. Any friend of Flamsteed was an enemy of Newton. Through Newton’s influence, Gray’s scientific career was over: he could not find a publisher or get scientific work of any kind.
Despite early successes and influential friends, Gray’s great work had to wait until after Newton’s death. In his sixties and living as a pensioner in Charterhouse, a home for destitute gentlemen, Gray returned to his electrical studies. He began experimenting with a glass electrical generator. The glass cylinder was sealed at one end with a cork to keep the dust out. Gray was ‘much surprised’ when he held a feather to the cork and discovered that the feather was attracted and repelled many times – just as it was by the rubbed glass. He concluded that an ‘attractive Vertue’ was ‘communicated to the Cork by the excited Tube’
This was truly surprising. Until then, it was assumed that the ‘electrical Vertue’ was a part of the rubbed object. Gray’s discovery was that electricity could move.
He then investigated how far the electrical ‘Vertue’ could be transmitted through wood:
Having by me an Ivory Ball of about one Inch three Tenths Diameter, with a Hole through it, this I fixed upon a Fir-Stick about four Inches long, thrusting the other End into the Cork, and upon rubbing the tube, found that the Ball attracted and repelled the Feather with more Vigour than the Cork had done.
Gray began investigating which materials could carry the ‘electrical Vertue’:
Then I made use of first iron, and then brass wire, to fix the ball on, inserting the other end of the wire in the cork, as before, and found that the attraction was the same as when the fir-sticks were made use of, and that when the feather was held over against any part of the wire, it was attracted by it, but though it was then nearer the tube, yet its attraction was not so strong as that of the ball.
Gray had discovered electrical conductors and insulators.
He extended his investigation further. Dangling eight metres of thread from a balcony to the floor below, he connected the top end to the generator and the bottom to the ivory ball. The ball attracted feathers. The string conducted the electricity.
Gray wanted to experiment with even longer threads, but did not have a high enough balcony. Instead he decided to lay the thread horizontally along a wooden floor. This did not work.
Eventually, he and Reverend Wheeler (a friend and supporter) suspended the conducting thread on fine dry silk threads. Using the silk as insulation, the range they were able to carry the electricity increased to more than one hundred metres.
Electrical demonstrations were popular in Enlightenment England. Stephen Gray published his results, and, I hope, made a little money, with an astonishing display of his electrical discovery.
Charterhouse, the home for impoverished gentlemen, had a school. This was convenient. Gray created an electrical demonstration that became famous across Europe and the new world. It involved dangling a small boy on silk strings and connecting him to an electrical generator. Charterhouse school provided the (presumably willing) volunteers.
Anyone who has had the opportunity to charge children to thousands of volts will appreciate the skill and showmanship of the dangling boy demonstration.
The boy was suspended from a wooden frame on the insulating silk strings and connected to the rotating glass generator by his foot. Feathers and chaff were attracted to the boy’s face from the ground. To anyone interested in electrical philosophy, this was amazing: electricity could be conducted.
Luckily for the boy, the full power of electricity to cause shock and pain had yet to be discovered. It took another fifteen years for the deadly Leyden jar to be discovered – twice.