Archive for the ‘History of Science’ Category

In a corridor adjacent to the foyer of the Clarendon Laboratory at the University of Oxford in England, is an electric bell that has been ringing almost continuously since it was first displayed in 1840.

OxfordElectricBell1The Oxford Electric Bell, also called the Clarendon Dry Pile, was an experimental electric bell when it was first set up. It consists of two brass half-spheres or bells, each positioned beneath a dry pile battery, with a metal sphere, about 4mm in diameter, suspended between the piles, acting as a ‘clapper’. The sphere moves the very short distance between the bells by electrostatic force. As the sphere touches one bell, it is charged by the pile, is electrostatically repelled, and is attracted to the other bell. On touching the other bell, the process repeats itself.

Whilst a high voltage is required to create the motion, only a miniscule amount of charge is carried from one bell to the other, which is why the piles have been able to last since the apparatus was set up. 

OxfordElectricBell2It is not known for sure what the piles are made of – they may be Zamboni piles which are made of alternate layers of metal foil and paper coated with manganese dioxide – but they were coated with molten sulphur to insulate them and to reduce the effects of atmospheric moisture.

clarendon laboratory, oxford university, physics

The original Clarendon Laboratory in Oxford (photo taken in 1894) was the first purpose-built physics laboratory in the country. The building, much enlarged, is now incorporated into the Department of Earth Sciences.

The bell was apparently made by Watkin and Hill, instrument makers, of London, and purchased by the Rev Robert Walker, Reader in Experimental Philosophy (the name by which physics was known at Oxford) at the university from 1839 to 1860, and Professor of Physics from 1860 to 1865. It bears a label in his handwriting ‘Set up in 1840’.

The Oxford Electric Bell does not demonstrate perpetual motion as the bell will eventually stop when the dry piles are depleted of charge, if the clapper does not wear out first. It has now been ringing almost continuously for 175 years apart from occasional short interruptions caused by high humidity. A double-thick glass bell jar muffles the ringing sound, so the bell is inaudible. There is a video of the bell here.

The bell has rung about 10 billion times and is considered to be the longest running experiment ever. The Guinness Book of Records lists it as the ‘world’s most durable battery’.

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pierre curie, marie curie, laboratory, paris, radioactivity, polonium, radium, uranium

Pierre and Marie Curie in their makeshift laboratory in Paris where they laboriously extracted minute quantities of the radioactive elements polonium (named after her native Poland) and radium from tonnes of uranium ore

On 26 December 1898, Marie and Pierre Curie working in a converted shed, formerly a medical dissecting room, in the Municipal School of Industrial Physics and Chemistry in Paris, announced their discovery of the radioactive element Radium. In the process Marie Curie coined the word radioactivity. The origin of the name Radium comes from the Latin word radius meaning ray. At the World Physics Congress in Paris in 1900, one of the results presented by the Curies was that their new substance glowed; materials containing radium emitted light as well as radioactive rays.

Between 1898 and 1902, the Curies published a total of 32 scientific papers, including one that announced that diseased, tumor-forming cells were destroyed faster than healthy cells when exposed to radium. The Curies published details of the processes they used to isolate radium, without patenting any of them, believing scientists should devote their lives to research for the benefit of humanity. In any case, they had no reason to expect that radium would be a big money-maker. But in the meantime a new industry began developing based on radium.

radium, ink, l d gardner, new york, radioactive, luminosity

A 1904 advert for radium ink manufactured by L D Gardner in New York. You are instructed to hold the picture in a bright light for a minute and then look at it in an absolutely dark closet.

Due to its therapeutic power, radium came to be seen as a source of life. After scientists successfully killed cancer cells with radium in early experiments in Europe, the demand for the element soared. In 1904 in New York, L D Gardner patented his radium ‘health’ water, Liquid Sunshine, and a glow-in-the-dark radium ink. Factories producing radium cures and novelty products began to appear all over the city. Quack doctors aggressively sold radium cures for almost every ailment with enormous success. By 1906, the so-called radium craze was sweeping through France, Britain, America, Germany and Italy. In the same year, a Los Angeles ‘doctor’ who sold radium and milk cures was sued for not using enough radium in his product. The radium craze even spread to the New York stage, where radium plays and dances featuring performers in glow-in-the-dark costumes were shown in theatres throughout the city. However, many critics suspected that the glowing costumes were not made of radium because of its prohibitively high cost, but of phosphorous

But while the controlled use of radiation was curing some cancers, its uncontrolled use by healthy people was another matter entirely. The trouble was that even pioneers such as the Curies knew nothing of the hazards. Early radiographers tested their X-ray machines on their hands each morning.

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