The Day the Universe Changed - James Burke [136]
Musschenbroek’s Leyden jar, the first electric capacitor. Water in a glass jar is electrified by contact with a brass wire attached to a gun barrel, charged by contact with a rotating glass globe rubbed by hand.
In 1753 Benjamin Franklin flew a kite in a thunderstorm to prove by the shocks he would receive that electricity was the same phenomenon as lightning. He too thought that electricity was a fluid which took positive and negative forms. All bodies possessed it. When overcharged, the recipient body became positive. When it was removed, the body became negative.
By the 1780s there were varying kinds of ‘imponderable fluids’such as positive and negative electricity, heat, light, austral and boreal magnetism, and so on. Could they be reduced to a smaller number of common ‘forces’, which either attracted or repelled?
In 1795 the first attempt to quantify electricity and magnetism was carried out by the Frenchman Charles de Coulomb. While looking for ways to improve operation of the compass, he found that a magnetic needle suspended on a thread could be used to measure electric and magnetic forces. The torsion balance, as it was called, showed that the forces, whatever they were, varied in strength relative to their distance from the source. They were also inversely proportional in strength to the square of their distance from the source. This was exactly the way in which gravity functioned, so it appeared to obey the laws of Newton. Coulomb also thought that electricity was composed of two fluids moving between bodies, while magnetism was made up of two fluids operating inside bodies. The two fluids were, however, different.
The problem so far, apart from ignorance of what the forces actually were, was their inadequate and irregular supply. An accident in Bologna provided a steadier source. While searching for proof that electricity existed in all forms of life, Luigi Galvani found that a shock from an electric ray fish was similar to that from a Leyden jar. Did animals generate the force? Between 1780 and 1786 Galvani concentrated on frogs, and noted that a frog’s leg would jerk when the nerves and muscles were in contact with two types of metal. It appeared that animals did indeed generate electricity.
Galvani’s animal experiments. In each specimen, nerves and muscles were put in simultaneous contact with two different metals which caused the muscles to contract and led Galvani to believe that electricity accumulated in muscle tissue.
A typical quack exponent of the fashionable craze for electrotherapy. The ‘commotions’induced by electricity were believed to inhibit ageing, restore drunkards to sobriety and cure innumerable ills, ranging from worms and lumbago to blindness and lockjaw.
Volta’s pile, made of a series of discs in the order zinc, wet paper, silver.
In nearby Pavia another Italian, Alessandro Volta, proved Galvani wrong. The electricity was being produced from the reaction between the two metals. Volta stacked discs of silver and zinc, interspersed with wet pasteboard, to produce a regular electrical current. Volta’s ‘pile’was the first battery to supply regular and consistent amounts of electricity.
With the publicity which the pile received began the difference in perception between the scientist and the man in the street about the nature of scientific advance. Within one year of the invention, science was to be seen sparking carbon rods to produce brilliant white arc light. In 1812 Russian mines were exploded across the river Neva at St Petersburg by German military experimenters. Electricity was being touted as a cure for all known conditions including fecundity and drowning. A close friend of Volta called Luigi Brugnatelli explored