LIEUT.-COL. ALEXANDER STRANGE, F.R.S, whose death we last week announced, was the fourth son of the late Sir Thomas Strange, and was born at Westminster on the 27th of April, 1818, and was educated at Harrow. On leaving school in 1834, at the early age of sixteen, he proceeded to India, and joined the 7th Regiment of Madras Light Cavalry, where his natural talents began to develop themselves. He shortly afterwards made the friendship of General Worster, who soon discovered that he had mechanical abilities of the highest order, and who subsequently instructed him in the use of astronomical and surveying instruments, and pointed out to him that nature had intended him for a scientific career. During the next few years he became a devoted student at the Magnetic and Meteorological Observatory at Simla, then under the direction of Major-General Boileau, R.E., at whose recommendation he was nominated, in 1847, by Col. (now Sir Andrew) Waugh, R.E., Surveyor-General of India, to the office of Second Assistant in the Great Trigonometrical Survey, where he found work suited to his talents. He was originally selected on account of his ability as an observer, and for his extraordinary mechanical skill, which in this department was of special value, and was displayed in such a remarkable degree as to call forth cae highest commendation from Col. Waugh. In the season 1848–49 he was attached to the party under Capt. (now Col.) Renny Tailyour, R.E., in order that he might acquire a practical knowledge of geodetical operations. Such was the rapidity with which he made himself master oi this difficult subject, that in 1850 he was promoted to the grade of First Assistant. Capt. Tailyour was ordered to undertake the triangu-lation of what is known as the “Karáchi Longitudinal Series,” which constitutes the southern flank of that considerable portion of the principal triangulation of the Survey of India known as the North-west Quadrilateral. It commences at Sironj in Central India, and terminates at Karáchi, in Sind. The extent of this arc of longitude is equivalent to 670 miles in length, covers an area of 23,000 square miles, and is one of the largest longitudinal arcs ever measured on the surface of the globe. At the end of the first season, Capt. Tailyour's services being required at head-quarters, Capt. Strange was ordered to take over the entire charge of the Series, and it is on this great undertaking that his fame as an Indian Surveyor rests. After crossing the Desert, over which the triangulation had to be carried nearly 200 miles, the work was carried on with the highest skill across the Plains of Sind, until at length, after much anxiety, and having overcome almost insuperable difficulties, the last angle which completed this great triangulation was measured on April 22, 1853, and the work brought to a successful close.