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Rh figure was crooked, his limbs shrunken; his hair hung in dishevelled locks over his haggard countenance. His temper was irritable, his habits penurious and solitary. He was, however, blameless in morals and reverent in religion. His scientific achievements would probably have been more striking if they had been less varied. He originated much, but perfected little. His optical investigations led him to adopt in an imperfect form the undulatory theory of light, to anticipate the doctrine of interference, and to observe, independently of though subsequently to F. M. Grimaldi (1618–1663), the phenomenon of diffraction. He was the first to state clearly that the motions of the heavenly bodies must be regarded as a mechanical problem, and he approached in a remarkable manner the discovery of universal gravitation. He invented the wheel barometer, discussed the application of barometrical indications to meteorological forecasting, suggested a system of optical telegraphy, anticipated E. F. F. Chladni’s experiment of strewing a vibrating bell with flour, investigated the nature of sound and the function of the air in respiration and combustion, and originated the idea of using the pendulum as a measure of gravity. He is credited with the invention of the anchor escapement for clocks, and also with the application of spiral springs to the balances of watches, together with the explanation of their action by the principle Ut tensio sic vis (1676).

His principal writings are Micrographia (1664); Lectiones Cutlerianae (1674–1679); and Posthumous Works, containing a sketch of his “Philosophical Algebra,” published by R. Waller in 1705.

HOOKER, JOSEPH (1814–1879), American general, was born in Hadley, Massachusetts, on the 13th of November 1814. He was educated at the military academy at West Point (1833–1837), and on graduating entered the 1st U.S. Artillery. In the war with Mexico (1846–48) he served as a staff officer, and rose by successive brevets for meritorious services to the rank of lieutenant-colonel. In 1853 he left the service and bought a large farm near Sonoma, Cal., which he managed successfully till 1858, when he was made superintendent of military roads in Oregon. Upon the opening of hostilities in the Civil War of 1861–65, he sacrificed his fine estate and offered his sword to the Federal Government. He was commissioned brigadier-general of volunteers on the 17th of May 1861 and major-general on the 5th of May 1862. The engagement of Williamsburg (May 5th) brought him and his subordinate Hancock into prominence, and Hooker received the soubriquet of “Fighting Joe.” He was engaged at the battle of Fair Oaks, and did splendid service to the Union army during the “Seven Days.” In the campaign of Northern Virginia, under General Pope (August 1862), he led his division with fiery energy at Bristoe Station, Manassas and Chantilly. In the Maryland campaign (September) he was at the head of the I. corps, Army of the Potomac, forced the defile of South Mountain and opened the way for the advance of the army. The I. corps opened the great battle of the Antietam, and sustained a sanguinary fight with the Confederates under Stonewall Jackson. Hooker himself was severely wounded. He was commissioned brigadier-general in the United States army on the 20th of September 1862, and in the battle of (q.v.), under Burnside, he commanded the centre grand division (III. and V. corps). He had protested against the useless slaughter of his men on that disastrous field, and when Burnside resigned the command Hooker succeeded him. The new leader effected a much-needed re-organization in the army, which had fought many battles without success. In this task, as in subordinate commands in battle, Hooker was excelled by few. But his grave defects as a commander-in-chief were soon to be obvious. By a well-planned and well-executed flanking movement, he placed himself on the enemy’s flank, but at the decisive moment he checked the advance of his troops. Lee turned upon him, Jackson surprised and destroyed a whole army corps, and the battle of Chancellorsville (see ), in which Hooker was himself disabled, ended in a retreat to the old position. Yet Hooker had not entirely forfeited the confidence of his men, to whom he was still “Fighting Joe.” The second advance of Lee into Union territory, which led to the battle of Gettysburg, was strenuously resisted by Hooker, who would have inflicted a heavy blow on Lee’s scattered forces had he not been condemned to inaction by orders from Washington. Even then Hooker followed the Confederates a day only behind them, until, finding himself distrusted and forbidden to control the movements of troops within the sphere of operations, he resigned the command on the eve of the battle (June 28, 1863). Faults of temper and an excessive sense of responsibility made his continued occupation of the command impossible, but when after a signal defeat Rosecrans was besieged in Chattanooga, and Grant with all the forces of the West was hurried to the rescue, two corps of the Army of the Potomac were sent over by rail, and Hooker, who was at least one of the finest fighting generals of the service, went with them in command. He fought and won the “Battle above the Clouds” on Lookout Mountain which cleared the way for the crowning victory of the army of the Cumberland on Missionary Ridge (see ). And in command of the same corps (consolidated as the XX. corps) he took part in all the battles and combats of the Atlanta campaign of 1864. When General McPherson was killed before Atlanta, the command of Grant’s old Army of the Tennessee fell vacant. Hooker, who, though only a corps commander, was senior to the other army commanders, Thomas and Schofield, was normally entitled to receive it, but General Sherman feared to commit a whole army to the guidance of a man of Hooker’s peculiar temperament, and the place was given to Howard. Hooker thereupon left the army. He was commissioned brevet-major-general in the United States army on the 13th of March 1865, and retired from active service with the full rank of major-general on the 15th of October 1868, in consequence of a paralytic seizure. The last years of his life were passed in the neighbourhood of New York. He died at Garden City, Long Island, on the 31st of October 1879.

HOOKER, SIR JOSEPH DALTON (1817– &emsp;&emsp; ), English botanist and traveller, second son of the famous botanist Sir W. J. Hooker, was born on the 30th of June 1817, at Halesworth, Suffolk. He was educated at Glasgow University, and almost immediately after taking his M.D. degree there in 1839 joined Sir James Ross’s Antarctic expedition, receiving a commission as assistant-surgeon on the “Erebus.” The botanical fruits of the three years he thus spent in the Southern Seas were the Flora Antarctica, Flora Novae Zelandiae and Flora Tasmanica, which he published on his return. His next expedition was to the northern frontiers of India (1847–1851), and the expenses in this case also were partially defrayed by the government. The party had its full share of adventure. Hooker and his friend Dr Campbell were detained in prison for some time by the raja of Sikkim, but nevertheless they were able to bring back important results, both geographical and botanical. Their survey of hitherto unexplored regions was published by the Calcutta Trigonometrical Survey Office, and their botanical observations formed the basis of elaborate works on the rhododendrons of the Sikkim Himalaya and on the flora of India. Among other journeys undertaken by Hooker may be mentioned those to Palestine (1860), Morocco (1871), and the United States (1877), all yielding valuable scientific information. In the midst of all this travelling in foreign countries he quickly built up for himself a high scientific reputation at home. In 1855 he was appointed assistant-director of Kew Gardens, and in 1865 he succeeded his father as full director, holding the post for twenty years. At the early age of thirty he was elected a fellow of the Royal Society, and in 1873 he was chosen its president; he received three of its medals—a Royal in 1854, the Copley in 1887 and the Darwin in 1892. He acted as president of the British Association at its Norwich meeting of 1868, when his address was remarkable for its championship of Darwinian theories. Of Darwin, indeed, he was an early friend and supporter: it was he who, with Lyell, first induced Darwin to make his views public, and the author of The Origin of Species has recorded his indebtedness to Hooker’s wide knowledge and balanced judgment. Sir Joseph Hooker is the author of numerous