The reputation of Chaptal as a chemist being well established, he was called to Paris in 1793, by the committee of public safety, to be consulted relative to the making of gunpowder and the production of saltpetre. It must be in the memory of all those who recollect the history of the first years of the French Revolution, that the want of saltpetre, the principal ingredient in gunpowder, had nearly put an end to the war; and as France had shut the ports of all nations against herself, no other resource remained but to produce the saltpetre at home. Before Chaptal was sent for, a manufactory, for this purpose, had been established at Grenelles, near Paris; but it was insufficient for the immense demand. Chaptal soon, by his skill and activity, so improved this establishment, that it supplied all that was wanted, and this at a time when France had about 1,400,000 soldiers.[3] [3] The theory of this artificial formation of saltpetre is detailed by Chaptal, in _Annales de Chimie_, tom. xx.--The bulk of saltpetre used in this country is brought from the East Indies, where, at certain seasons of the year, it is found deposited on the surface of the soil. It is swept off once or twice a week, and as often renewed. At Apulia, near Naples, there is a bed containing 40 per cent. of it; and in Switzerland the farmers extract it in abundance from the earth under the stalls of the cattle. In the reign of Charles I. great attention was paid to the making of saltpetre in England. Certain patentees were authorized by royal proclamation to dig up the floors of all dove-houses, stables, &c. In France, the plaster of old walls is washed to separate the nitrate of lime, which is a soluble salt, and this, by means of potash, or muriate of potash, is afterwards converted into nitre. Mr. Bowles, in his Introduction to the Natural History of Spain, assures us there is enough saltpetre in that country to supply all Europe for ever. Chaptal returned to Montpellier in 1794, and soon obtained a place in the administration of the department of Herault, and a professorship of chemistry in the university of Montpellier, which the Directory created expressly as a reward for his services. In 1798, Chaptal revisited Paris, and aided the Revolution by which, in 1799, Buonaparte became First Consul. In the following year Chaptal was made Minister of the Interior, in which important office he imparted new energy to all the manufacturing establishments of France, as well as founded many public schools upon improved systems of education. In 1804 he was dismissed from the Ministry for his refusing to sanction a report stating sugar from beet-root to be superior to that from the cane.[4]