ENGINEERING in its early uses referred specially to the operations of those who constructed engines of war and executed works intended to serve military purposes. Such military engi neers were long the only ones to whom the title was applied. But about the middle of the 18th century there began to arise a new class of engineers who concerned themselves with works which, though they might be in some cases, as in the making of roads, of the same character as those undertaken by military engineers, were neither exclusively military in purpose nor executed by soldiers, and those men by way of distinction came to be known as civil engineers. No better definition of their aims and functions can be given than that which is contained in the charter (dated 1828) of the Institution of Civil Engineers (London) , where civil engi neering is described as the "art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states, both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation and docks for internal intercourse and exchange, and in the construction of ports, harbours, moles, breakwaters and lighthouses, and in the art of navigation by artificial power for the purposes of commerce, and in the con struction and adaptation of machinery, and in the drainage of cities and towns." Wide as is this enumeration, the practice of a civil engineer in the earlier part of the 19th century might cover many or even most of the subjects it contains. But gradually specialization set in. Perhaps the first branch to be recognized as separate was mechanical engineering, which is concerned with steam-engines, machine tools, mill-work and moving machinery in general, and it was soon followed by mining engineering, which deals with the location and working of coal, ore and other miner als. Subsequently numerous other more or less strictly defined groups and subdivisions came into existence, such as marine, sanitary, chemical, electrical, and aeronautical engineering.