Page:Popular Science Monthly Volume 42.djvu/717

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hibitions, while the intensity of the current was so low that hardly a visible spark could be made to pass by it through poles of carbon. The magnetic effects were afterward shown by Prof. Henry to be attainable from a single cell, if combined with suitable conductors. Instead of Cruikskank's cumbrous battery of alternating zinc and copper plates, which Davy used in the experiments that resulted in the discovery of the metallic bases of the alkalies, Hare found a way of obtaining a corresponding amount of surface and its resultant power with a single roll of metal, and in 1820 introduced the denagrator, in which any series, however extended, could be instantaneously brought into action or rendered passive, at pleasure. This apparatus consists of a large sheet of copper having several hundred square feet of surface and a similar one of zinc, separated by a piece of felt or cloth saturated with acidulated water, and then rolled up in the form of a cylinder. Faraday bore testimony, in his Experimental Researches, to the merit of this invention when, in 1835, he acknowledged that, having worked exhaustively to perfect the voltaic battery, finding that Hare had anticipated him many years before, and had accomplished all that he had attempted, he at once adopted his instruments, as embodying the best results then possible.

With one of Hare's deflagrators, Prof. Silliman, in 1823, first demonstrated the volatilization and fusion of carbon, a result then considered so extraordinary that it was a considerable time before it was fully credited. It was with these batteries that the first application of voltaic electricity to blasting under water was made in 1831 in experiments conducted under Dr. Hare's direction.

Dr. Hare was also distinguished in chemistry as the author of a process for denarcotizing laudanum, and of a method for detecting minute quantities of opium in solution. He was interested, too, in the discussions of philosophical chemistry, as was most notably shown in the earnestness with which he contested what he conceived were the errors of the salt radical theory.

He made studies in meteorology, and had a theory of whirlwinds and storms founded on an electrical hypothesis, which he opposed to the rotary theory of W. C. Redfield. At the second meeting of the American Association for the Advancement of Science he explained his own views on this subject, while he controverted those of Mr. Redfield. This gentleman was present and heard his remarks, but made no reply then. He was not a speaker, and did not address the public except in writing.

In 1818 Dr. Hare was chosen Professor of Chemistry and Natural Philosophy in William and Mary College, and in the same year was made Professor of Chemistry in the medical department of the University of Pennsylvania. He held the latter position till 1817. His teachings were marked by the originality of his