PHILO, a celebrated writer on mechanics, was a native of Byzantium, and flourished in the year 160, being the contemporary of Ctesibius and Hero. He was the author of a work entitled Poliorectica, on the method of attacking and defending towns, of which the fourth and fifth books have been preserved. The first treats of the manner of preparing arrows, balistæ, catapultæ, and other warlike engines. Amongst other inventions, he mentions a machine of Ctesibius which discharged weapons by means of compressed air, upon the same principle, no doubt, as our air-gun. In the second book he treats of the manner of fortifying and provisioning cities, and, amongst other things, recommends that the provisions and water be poisoned if there be danger of the place falling into the hands of an enemy. This work has been published, with a Latin translation, in a collection entitled Veterum Mathematicorum Opera, Par. 1693. The invention of the air-gun has been treated of by Albinus Meister, De Catapulta polybola Commentatio qua locus Philonis Mechanici, in libro iv. de telorum constructione certans illustratur, Göttingen, 1768. There is another little work attributed to Philo, entitled De septem Orbis Spectaculis, part of the sixth chapter of which, and the whole of the seventh, are lost. It has been published, with a Latin translation, and many learned notes, by J. C. Orelli, Leipzig, 1816, 8vo.