ARNOLD, Isaac Newton, lawyer, born in Hartwick, Otsego County, New York, 30 November 1815; died in Chicago, 24 April 1884. His father, Dr. George W. Arnold, was a native of Rhode Island, whence he removed to western New York in 1800. After attending the district and select schools, Isaac Arnold was thrown on his own resources at the age of fifteen. For several years he taught school a part of each year, earning enough to study law, and at the age of twenty was admitted to the bar. In 1836 he removed to Chicago, where he spent the rest of his life, and was prominent as a lawyer and in politics. He was elected city clerk of Chicago in 1837, and, beginning in 1843, served several terms in the legislature. The state was then heavily in debt, and Mr. Arnold became the acknowledged champion of those who were opposed to repudiation. In 1844 he was a presidential elector, and in 1860 was elected to congress as a republican, serving two terms. At the battle of Bull Run he acted as volunteer aide to Colonel Hunter, and did good service in caring for the wounded. While in congress he was chairman of the committee on the defenses and fortifications of the great lakes and rivers, and afterward chairman of the committee on manufactures, serving also as member of the committee on roads and canals. tie voted for the bill abolishing slavery in the district of Columbia, and in March 1862, he introduced a bill prohibiting slavery in every place under national control. This bill was passed on 19 June 1862, after much resistance, and on 15 February 1864, Mr. Arnold introduced in the House of Representatives a resolution, which was passed, declaring that the constitution of the United States should be so amended as to abolish slavery, his ablest speech in congress was on the confiscation bill, and was made 2 May 1862. In 1865 President Johnson appointed him sixth auditor to the United States treasury. Mr. Arnold was an admirable public speaker, and delivered addresses before various literary societies, both at home and abroad. He had been intimate with Abraham Lincoln for many years before Mr. Lincoln's election to the presidency, and in 1866 he published a biography of him (new ed., rewritten and enlarged, Chicago, 1885). This was followed in 1879 by a " Life of Benedict Arnold," which, while acknowledging the enormity of Arnold's treason, vindicates and praises him in other respects. The author claimed no relationship with the subject of his work. His life of Lincoln is valuable for the clearness with which it shows the historical relations of the president to the great events of his administration; and the author's death is said to have been caused, in part, by his persistent labor in completing his last revision of this work. Mr. Arnold was for many years president of the Chicago historical society, and Hen. E. born Washburne delivered an address on his life before the society, 21 October 1884 (Chicago, 1884).