Joule

jool, James (1818-1889), an English physicist. He was a native of Lancashire. His father was a brewer. He was in part a self educated man, but came under the influence of the celebrated Dalton. His life work was a long series of experiments on the relations that exist between heat and energy. One of his experiments is easily understood. He attached a weight to a cord wound on an axle, and connected the axle with a series of paddles turning in a quantity of water contained in a reservoir, like a churn. As the weight descended, the paddles worked in the water. He found that the descent of the weight and the churning of the water heated the water. After making due allowance for loss of energy by friction and loss of heat by condensation, he decided that the descent of 772.55 pounds one foot, or one tenth that weight ten times as far, etc., would raise the temperature of a pound of water 1 deg. F. In other words, he established the doctrine, known as Joule's Law, that 772.55 units of mechanical energy are equivalent to 1 unit of heat. The converse of this statement is applicable to the operation of steam engines. The heat required in raising the temperature of a pound of water 1 deg. F. is capable of raising a weight of one pound 772.55 feet. The interchangeability of heat and work is called the doctrine of the conservation of energy. It applies as well to other forms of energy, as light and electricity. In accordance with Joule's Law the scientist can tell beforehand how much heat, light, or electricity a piece of coal is capable of producing, and how much work it can do. Joule received honors and membership in the leading scientific societies of the world, and in 1873 was made president of the British Association for the Advancement of Science. His leading doctrine was announced in a paper read in 1847 at Manchester, England.