The supply from the caves proved insufficient, and artificial nitre beds or nitraries were prepared in the cities of south and central Alabama. It was necessary to have them near large towns, in order to obtain a plentiful supply of animal matter and potash, and the necessary labor. Efforts were also made to induce planters in marl or limestone counties to work plantation earth.[367] Under the supervision of Professor W. H. C. Price, nitraries were established at Selma, Mobile, Talladega, Tuscaloosa, and Montgomery. Negro labor was used almost entirely, each negro having charge of one small nitre bed. To October, 1864, the nitraries of south Alabama produced 34,716 pounds at a cost of $26,171.14, which was somewhat cheaper than the nitre from the caves. From these nitraries better results were obtained than from the French, Swedish, and Russian nitraries which served as models. The Confederate nitre beds were from sixteen to twenty-seven months old in October, 1864, and hence not at their best producing stage. Yet, allowing for the difference in age, they gave better results, as they produced from 2.57 to 3.3 ounces of nitre per cubic foot, while the average European nitraries at four years of age gave 4 ounces per cubic foot. Earth from under old houses and from cellars produced from 2 to 4 ounces to the cubic foot. Nitre caves produced from 6 to 12 ounces per cubic foot. Most of the nitre thus obtained was made into powder at the mills in Selma. There were some private manufacturers of nitre, and to encourage these the Confederate Congress authorized the advance to makers of fifty per cent of the cost of the necessary machinery.[368] The state legislature appropriated $30,000 to encourage the manufacture and preparation of powder, saltpetre (nitre), sulphur, and lead. Little of the last article was found in Alabama.[369] Some of the powder works were in operation as early as 1861, and in that year the War Department gave Dr. Ullman of Tallapoosa a contract to supply 1000 to 1500 pounds of sulphur a day.[370]