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 HERSENT ifine his attention to astronomy. He calcu- lated the density of the atmosphere, and held that a perfect vacuum exists at the height of 80 or 90 miles above the earth, and also that three fourths of all the atmospheric air is within four miles of the earth's surface. The question concerning the absorption of light, which gave rise to much discussion, particu- larly in its connection with the undulatory theory, was very ably answered by Herschel in his paper on the " Absorption of Light by Col- ored Media." He made some important dis- coveries in photography, and produced from chemical compounds and the juices of plants the most beautiful chromatic "eifects. Sir John Herschel contributed to the " Manual of Scientific Inquiry " (1849 and 1851), and wrote "Outlines of Astronomy" (1850; 10th ed., 1869); "Essays, from the Edinburgh and Quarterly Reviews, with Addresses and other Pieces " (185V) ; " Physical Geography '' (1861) ; and " Familiar Letters on Scientific Subjects " (1866). His son, Capt. John Herschel of the royal engineers, is now (1874) collecting his letters with a view to publication. During the year 1848 Herschel was president of the royal astronomical society. In 1850 he was ap- pointed master of the mint, which office he held till 1855, when he resigned on account of ill health. In 1855 he became one of eight foreign associates of the French academy of science. HERSENT, Louis, a French painter, born in Paris, March 10, 1777, died there, Oct. 2, 1860. He studied under Regnault, and at the age of 20 gained the second prize at the school of fine arts. He was one of the painters to the government, and received an honorary decoration from Louis XVIII., who bought his " Ruth and Boaz " and " Monks of St. Ber- nard." His " Abdication of Gustavus Vasa," considered his best work, was destroyed in the sacking of the Palais Royal in 1848. His "Louis XVI. giving Alms to the People," now in the museum -at Versailles, was among his later works. Almost all his pictures have been engraved. HERSFELD, a town of Prussia, in the prov- ince of Hesse-Nassau, 10 m. N. N. E. of Fnl- da, on the left bank of the Fulda; pop. in 1871, 6,434. It owes its origin to a Benedictine ab- bey which was founded in the 8th century. "With its territory it was made an ecclesiastical principality in the 12th century, under the gov- ernment of the abbots. At the peace of West- phalia (1648) it was secularized, and the town of Hersfeld remained the capital till 1821, when the principality became an administrative cir- cle. The town until lately was walled, and protected with an ancient ditch ; gardens are now laid out in place of these. The river is here crossed by two bridges. Among the note- worthy buildings are the ancient council house, the fine parish church with a lofty tower and a great bell, and the ruins of the convent church which was built in the beginning of the 12th HERTFORDSHIRE 701 century, in the Byzantine style, on the site of the cathedral which had been burned. The ancient monastery itself, shut off from the town, has its own district, containing the ruins of the church and the surrounding gardens and or- chards. The gymnasium was founded in 1570 by Abbot Michael. Hersfeld is the head of the cloth manufactures of the former electorate of Hesse, employing 2,000 hands, and has manu- factories of mixed cotton goods, soap, and red and white leather, and numerous dye works and worsted mills. IIERSTAL, a town of Belgium, in the province and 3 m. N. E. of the city of Liege, on the left bank of the Meuse; pop. in 1866, 9,326. Va- rious kinds of iron and steel ware, especially firearms, are manufactured in the town, which has also an establishment for the extraction of pyroligneous acid, a salt refinery, breweries, &c. In the neighborhood are many coal mines. Herstal was the home of Pepin the Fat, gen- erally called Pepin of Heristal. HERTFORD, a N. E. county of North Carolina, bordering on Virginia, bounded E. by Chowan and Nottoway rivers, and intersected by the Meherrin, which unites with the Nottoway to form the Chowan ; area, 320 sq. m. ; pop. in 1870, 9,273, of whom 4,952 were colored. It has a level surface, covered in part with pine and cedar woods, which furnish large quantities of timber, tar, and turpentine for exportation. The Chowan river is navigable by sloops along the border of the county. The chief produc- tions in 1870 were 5,4*30 bushels of wheat, 189,079 of Indian corn, 13,857 of oats, 49,807 of sweet potatoes, and 235 bales of cotton. There were 915 horses, 1,174 milch cows, 2,708 other cattle, 2,259 sheep, and 11,398 swine; 1 saw mill, and 7 flour mills. Capital, "Winton. HERTFORD, a town and parliamentary bor- ough of England, capital of Hertfordshire, on the river Lea, 18 m. N. of London; pop. in 1871, 7,164. It has eight churches, a Latin school, a mechanics' institute, a branch of the London Christ's hospital, a large distillery, and several large breweries. There is an active trade in coal, timber, and corn. In 673 a na- tional ecclesiastical council was held here, and early in the 10th century Edward the Elder rebuilt the town and built the castle, which afterward was occasionally a royal residence. HERTFORDSHIRE, or Herts, an inland county of England, bordering on Cambridgeshire, Es- sex, Middlesex, Buckinghamshire, and Bed- fordshire ; area, 611 sq. m. ; pop. in 1871, 192,226. Its principal rivers are the Colne and Lea with their tributaries, affluents of the Thames, and some smaller streams flowing to the Ouse. Part of the New river, which sup- plies London with water, is within the shire, and is conducted by an aqueduct along the val- ley of the Lea. The Grand Junction canal passes through the county. It is also traversed by the London and Northwestern and Great Northern railways, while the Eastern Counties railway skirts the S. E. boundary. In the