QUINBY, Isaac Ferdinand, soldier, born near Morristown, New Jersey, 29 January, 1821. He was graduated at the United States military academy in 1843, standing first in engineering. He was a classmate and close friend of General Grant. He was an assistant professor at West Point in 1845-'7 and took part in several skirmishes on the Rio Grande and Vera Cruz lines at the close of the Mexican war. He went to Rochester, New York, in September, 1851, to become professor of mathematics in the newly founded university in that city, and resigned from the army, 16 March, 1852. He held his professorship until the civil war, and then became colonel of the 13th New York regiment. Under his command, it marched through Baltimore on 30 May, being the first body of National troops to pass through that city after the attack upon the 6th Massachusetts regiment on 19 April. Colonel Quinby resigned his commission, 2 August, 1861, and resumed his chair; but he was appointed brigadier-general of voluteers, 17 March, 1862, and in the following" month was assigned to the command at Columbus, Kentucky In October, 1862, he was relieved, to take command of the 7th division of the Army of the Tennessee. The division was sent to take part in the movement to turn the Confederate right flank at Vicksburg by Yazoo pass, the Cold-water, Tallahatchie, and Yazoo rivers. Amid great difficulties General Quinby pushed on to Fort Peruberton, where he arrived on 23 March. Finding that there was no ground suitable for camping or moving a large body of troops, and the fire of the small gun-boats being ineffectual, he conceived the idea of going around to the east side of Fort Pemberton, crossing the Yallabusha river on a pontoon bridge, cutting the communications of the fort, and compelling its surrender: but he also constructed works for a direct attack, and sent back to Helena for heavy guns. The boat that carried them brought orders from General Grant to abandon the movement by Yazoo pass, and General Quinby withdrew his force from before Fort Pemberton on 5 April. The fatigues and anxieties of this expedition in a malarious region brought on a severe illness, and he was ordered home on sick-leave, 1 May, 1863. But learning, a few days after reaching home the progress of Grant's movement to the rear of Vicksburg, he hastened back, assuming command of his division on the 17th, and taking part in the assault of the 19th, and the subsequent movements. On 5 June illness again rendered him unfit for duty in the field, and he went to the north under Grant's orders, remaining in Rochester until 1 July. He then commanded the rendezvous at Elmira till 31 December, 1863, when, convinced that he would not again be able to go to the front, he resigned his commission and resumed his duties as professor in the university. In May, 1869, he was appointed United States marshal for the northern district of New York, and he held that office during General Grant's two presidential terms, holding his professorship also till September, 1884. In May, 1885, he was appointed city surveyor of Rochester, and he now (1888) holds that office. He was a trustee of the Soldiers' home at Bath. New York, and vice-president of the board from the foundation of the institution in 1879 till his resignation in 1886. In addition to his official duties, he is frequently employed as a consulting engineer. He has revised and rewritten several of the works in the Robinson Course of Mathematics, and the treatise on the "Differential and Integral Calculus" in that series is altogether his.