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a description of a microscopic compass
invented by him.
His greatest achievement was the invention of the " Electric Chrono- graph," or "Magnetic Clock." Lieut. Maury, in an official letter to the Hon. John Y. Mason, secretary of the navy, dated National Observatory, Wash- ington, January 5, 18-49, says: "I have the honor of making known to you a most important discovery in astron- omy, by Dr. Locke, of Ohio." After his observations in magnetism had been published, the English govern- ment presented to him a complete set of magnetic instruments.
After his return to Cincinnati in 1S55, he broke down completely. For rest he went to Virginia to examine some coal lands, but returned with his infirmities greatly aggravated.
He married, in Cincinnati, October 25, 1825, Miss Mary Morris, of New- ark, New Jersey.
He was author of "The Outlines of Botany" (1829); A sub-report on "The Survey of the Mineral Lands of Iowa, Illinois, and Wisconsin," pub- lished by Congress (1840); sub-report on "The Geology of Ohio," pubhshed by the state (1838); and text-books on botany and English grammar.
He died in Cincinnati, July 10, 1856.
A. G. D.
From an address on the Life and Character of Professor John Locke," by M. B. Wright, M. D., 1857.
Logan, George (1753-1821).
George Logan, son of William and grandson of James Logan, the distin- guished friend and secretary of William Penn, was born at Stenton, near Phila- delphia, September 9, 1753. He was sent to England for his education when very young, and, on his return, served an apprenticeship with a merchant of Phila- delphia. He had early a great desire to study medicine, which he undertook after he had attained to manhood. After spending three years at the medical School of Edinburgh, he travelled through
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France, Italy, Germany and Holland, and returned to his own country in 1779.
He applied himself for some years to agricultuie, and was active in securing and exchanging seeds and plants with the leading botanists. He married Martha, the fifteen-year old daughter of Robert Daniel, of South Carolina, and she was an equally enthusiastic botanist, writing a treatise on gardening when seventy years of age. Pie also served in the Legislature. In June, 1798, he embarked for Europe for the purpose of preventing a war between France and America. For this step he was violently denounced by hostile partisans, but he persevered and succeeded in his intentions. He was a Senator from Pennsylvania in the Con- gress of the United States, from 1801 to March, 1807. In 1810 he visited Eng- land — as formerly France — with the same philanthropic desire of preserving peace between the two countries. He was exceedingly grieved at the war which followed, his health gradually declined for some years, and he died April 9, 1821.
Memorials of John Bartram and Humphrey Marshall, William DarHngton, 1849.
Logan, Samuel (1831-1893).
Samuel Logan, surgeon, was born near Charleston, South Carolina, on April 16, 1831, a Scotsman his father, his mother a Glover of South Carolina. The boy was educated in his native city and graduated from the South Carolina Medical College in 1853, prac- tising but a few months in Charleston, where he was appointed assistant demon- strator of anatomy in his alma mater. A year later he became professor of anatomy and lectured on surgery in the summer school until the outbreak of the Civil War, when he volunteered his ser- vices to the Confederacy.
In 1865 and 1866 he resumed his duties in the chair of anatomy and surgery at the South Carolina Medical College and the following summer became professor of anatomy in the Medical College of Richmond, Virginia, accepting the chair of surgery in the
