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494 study of electricity. As early as 1820 he had invented a new method of arranging the lightning conductors of ships, the peculiarity of which was that the metal was per manently fixed in the masts and extended throughout the hull; but it was only with great difficulty, and not till nearly thirty years afterwards, that his invention was adopted by the Government for the royal navy. In 1826 he read a paper before the Royal Society &quot;On the Relative Powers of various Metallic Substances as Conductors of Electricity,&quot; which led to his being elected a member of the society in 1831. Subsequently, in 1834, 1836, and 1839, he read be fore the society several valuable papers on the elementary laws of electricity, and he also communicated to the Royal Society of Edinburgh various interesting accounts of his experiments and discoveries in tlie same field of inquiry. In 1835 he received the Copley gold medal from the Royal Society for his papers on the &quot; Laws of Electricity by High Tension,&quot; and in 1839he was chosen to deliver the Bakerian lecture. Meanwhile, although a Government commission had recommended the general adoption of his conductors in the royal navy, and the Government had granted him an annuity of 300 &quot; in consideration of services in the cultivation of science,&quot; the naval authorities continued to offer various objections to his invention ; to aid in re moving these he in 1843 published his work on Thunder storms, and also about the same time contributed a number of papers to the Nautical Magazine illustrative of damage by lightning. His system was actually adopted in the Russian navy before he succeeded in removing the pre judices against it in England, aud in 1845 the emperor of Russia in acknowledgment of his services presented him with a valuable ring and a superb vase. At length, every doubt as to the efficiency of his system having been removed, he received in 1847 the honour of knighthood, and subsequently a grant of 5000. After succeeding in introducing his invention into general use Harris resumed his labours in the field of original research, but as he failed to realize the advances that had been made by the new school of science his application resulted in no discoveries of much value. His manuals of Electricity, Galvanism, and Magnetism, contributed to Weale s rudimentary series, were however written with great clearness, and passed through several editions. He died 22d January 1867, while having in preparation a Treatise on Frictional Electricity, which was published posthumously in the same year, with a memoir of the author by Charles Tomlinson, F.R.S.  HARRISBURG, a city of the United States, capital of Dauphin county and of the State of Pennsylvania, is beautifully situated on the east bank of the Susquehanna river, on the Pennsylvania canal, and at the junction of several railways, 126 miles by rail N. of Washington and 105 W. by N. of Philadelphia. The river, which is here a mile in width, is crossed by two bridges, one of which is for the use of the railways. Two other bridges of great beauty and strength span the river in view of the State-house. The State buildings, dating from 1819, occupy an eminence in the centre of the busiest portion of the city, and consist of the State capitol, 180 feet long by 80 feet wide, with a circular portico in front sup ported by six Ionic columns and surmounted by a dome, and, on two sides of the capitol, smaller buildings uniform in design, .containing the executive chamber, the State treasury, and various other offices. The capitol park con tains a monument to those who died in the Mexican war. Among the other public buildings are the county court house, the State arsenal, the county prison, and the opera-house. Harrisburg is a bishop s see of the Roman Catholic Church. It is well provided with academies and schools, and possesses about 30 churches, several of which are costly and ornamental edifices. It is also the seat of the State library of over 40,000 volumes. Among the benevolent institutions are the city hospital, the home for the friendless, and the State lunatic hospital. An abundant water supply is obtained from the river. Coal and iron are largely wrought in the neighbourhood, and the great facilities of communication both by canal and railway have enabled the city to become one of the centres of the iron trade. It possesses large iron-foundries, manu factories of steel, machines, boilers, engines, carriages, nails, files, galvanized iron, brooms, soap, and shoes, rolling-mills, saw and planing mills, flour-mills, cotton- mills, potteries, tanneries, and breweries. The inhabi tants in 1860 numbered 13,405, and in 1870 23,104. The population of the city proper for 1880 is estimated at 31,700, and that of the suburbs at 4900, making a total of 36,600.

1em  HARRISON, (1693–1776), an eminent mechani cian, was the son of a carpenter, and was born at Faulby, near Pontefract, in Yorkshire, in the year 1693. Thence his father and family removed in 1700 to Barrow, in Lincoln shire. Young Harrison at first learned his father s trade, and worked at it for several years, at the same time occasionally making a little money by land-measuring and surveying. The strong bent of his mind, however, was towards mechanical pursuits; and this showed itself specially in endeavours to improve the construction of clocks and watches so as to render them more accurate measurers of time. He soon learned that, to enable a clock to keep accurate time, the pendulum must be so con structed as to preserve the distance between the point of suspension and centre of oscillation invariable, notwith standing the expansion and contraction of the rod caused by changes of temperature. To accomplish this Harrison de vised, in 1726, his ingenious &quot;gridiron pendulum,&quot; which consists in having the bob suspended by a series of parallel rods, alternately of steeland brass, so arranged that the down ward expansion of the steel rods from change of tempera ture is exactly compensated for by the upward expansion of the brass rods. This principle of compensation, modi fied to suit particular cases, is now applied to all good watches and chronometers. Another ingenious improve ment in clockmaking devised by Harrison was his recoil escapement, which obviated the necessity of keeping the pallets well oiled. He was led to invent this, as he himself tells us, by having on one occasion had to go a long dis tance to set right a turret clock which had stopped simply from want of oil on the pallets. This escapement, although answering admirably the intended purpose, is rather too delicate to be adopted in ordinary practice. Harrison was also the first to employ the commonly used and effective form of &quot; going ratchet,&quot; which is a spring arrangement for keeping the timepiece going at its usual rate during the interval of being wound up. In Harrison s time the Government of the country had become fully alive to the necessity of determining more accurately the longitude at sea. For this purpose they passed an Act in 1714 offering rewards of 10,000, 15,000, and 20,000 to any who should construct chronometers that would determine the longitude within 60, 40, and 30 miles respectively. Harrison applied him self vigorously to the task, and in 1735 went to the Board of Longitude with a watch which he also showed to Halley, Graham, and others. Through their influence he was allowed to proceed in a king s ship to Lisbon to test 