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COLBURN COLCHESTER tain. At this time he was unable to give any account of the mental processes by which these results were reached ; but a few years later he could explain them satisfactorily, and from these explanations it appeared that his process- es did not differ materially from those ordina- rily adopted in mental computation. Among the questions proposed to him were the follow- ing: How many days and hours in 1,811 years? His answer, given in 20 seconds, was 661,015 days, 15,864,360 hours. How many seconds in 11 years? The answer, given in four seconds, was 346,896,000. When 8 or 9 years of age, he gave answers with a delay of but a few sec- onds to such questions as these : What is the square of 999,999 ? Multiply the square twice by 49 and once by 25. (The answer requires 17 figures.) What are the factors of 4,294,- 967,297 ? (=2 sa + 1). The French mathemati- cians had announced this as a prime number. Colbnrn immediately gave 641 x 6,700,417. What are the factors of 247,483 ? He replied, " 941 and 263, which are the only factors." The rapidity of his mental processes and the power of his memory must have been at this time almost inconceivable. After leaving Bos- ton, Mr. Colburn exhibited his son for money throughout the middle and part of the southern states, and in January, 1812, sailed with him for England. After travelling over England, Scotland, and Ireland, they spent 18 months in Paris. Here young Colburn was placed in the lycee Napoleon, but was soon removed by his father, who at length, in 1816, returned to Eng- land in the deepest penury. The earl of Bris- tol soon became interested in the boy, and placed him in Westminster school, where he remained till 1819. In consequence of his father's refusal to comply with certain arrange- ments proposed by the earl, he was removed from Westminster, and Mr. Colburn now pro- posed to his son that he should qualify himself to become an actor. Accordingly, he studied for this profession, and was for a few months under the tuition of Charles Kemble. His first appearance, however, satisfied both his in- structor and himself that he was not adapted for the stage, and accordingly he accepted a situation as assistant in a school, and soon afterward commenced a school of his own. To this he added the performing of some as- tronomical calculations for Dr. Thomas Young, then secretary of the board of longitude. In 1824, on the death of his father, he was en- abled by the earl of Bristol and other friends to return to America. He went to Fairfield, N. Y., as assistant teacher of an academy ; but not being pleased with his situation, he re- moved in March following to Burlington, Vt., where he taught French, pursuing his studies at the same time in the university. Toward the end of 1825 he connected himself with the Methodist church, and after nine years of ser- vice as an itinerant preacher, he settled in Norwich, Vt, in 1835, where he was soon after appointed professor of languages in Nor- wich university. In 1833 he published his autobiography. From this it appears that his faculty of computation left him about the time he reached the age of manhood ; and aside from his early talent for calculation, he gave no evi- dence of remarkable abilities. COLBY, Thomas, an English engineer, born at Rochester, Sept. 1, 1784, died in Liverpool, Oct. 9, 1852. He was educated at the royal military academy at Woolwich, and received his first commission as second lieutenant of engineers when 17 years old. The next year he became chief personal assistant of Captain Mudge, then superintendent of the ordnance survey. During the four following years he passed the summers in making observations at various prominent points, and the winters in preparing the results for publication and super- intending the engraving of the ordnance maps. He became identified with the great trigonome- trical survey of England, and upon the publica- tion of the third volume of the records his name appeared associated with that of Col. Mudge upon the title page. In 1807 he was raised to the rank of captain. In 1813 it was determined to extend the meridian line into Scotland, and Capt. Colby was placed in charge of the work. In 1817 he accompanied Biot, a scientific agent of the French government, on his trip to Shetland, and afterward assisted in connecting the French with the English tri- angulation by observations across the straits of Dover. Upon the death of Gen. Mudge in 1820, Colby was appointed his successor as su- perintendent of the survey and in the board of longitude, was elected a fellow of the royal society, and promoted to the rank of major, and soon after to that of lieutenant colonel. Hav- ing undertaken a thorough survey of Ireland, he received the sanction of the duke of Wel- lington for raising and training three compa- nies of sappers and miners to aid in the work. After a series of experiments on the heating and cooling of metallic rods, he succeeded in so uniting a bar of brass and iron that its extrem- ities always remained the same distance apart whatever the temperature. With this " com- pensation bar" he measured a base line of eight miles on the south side of Lough Foyle ; and such was the exactitude obtained that the same apparatus has since been used in the re- measurement of the English bases, in measuring a base at the Cape of Good Hope, and also those required for the great arc of the meridian in India. Col. Colby continued his superin- tendence of the survey till his promotion in 1846 to the grade of major general, when by the regulations of the service his active connec- tion with it ended. He had brought English maps to an excellence not before attained, marking the seconds of latitude and longitude on the margin, and introducing into them geological facts and features. COLCHESTER, a municipal and parliamentary borough, market town, and river port of Essex, England, on the river Colne, and the Great