Without detailing minutely the processes employed for extracting sulphur from its combinations, which may be seen in Thenard, (_Traité de Chimie_, tome i, p. 184) it will be sufficient to observe, that, in general, pyrites, both of iron and copper, are arranged in alternate layers in the form of a pyramid, and the _roasting_ is continued for several months. Part of the sulphur is consumed, and part is sublimed, and is condensed and collected in hollows, in the upper part of the pyramid, whence it is removed several times a day. It is also obtained from pyrites, by a kind of distillation. They are reduced to coarse powder, and put into hollow iron cylinders, or retorts, where the sulphur is disengaged and melted, and thence runs into vessels of water. This process is employed in Saxony, where nine hundred pounds of pyrites will yield one hundred to one hundred and fifty pounds of sulphur, which is afterwards purified. When melted and cast into wooden moulds, it forms the roll brimstone; and, by sublimation, conducted in large chambers, as we shall afterwards mention, it is converted into the flowers of sulphur. The residue of the sublimation is _sulphur vivum_, which is also used in fire-works. The roll brimstone is frequently adulterated. In the island of Anglesea, it is obtained by the sublimation of the yellow copper ore. The operation is conducted in kilns, and the sulphur is conveyed by means of long horizontal flues, and collected in large chambers. As the United States furnish an abundance of martial pyrites, and also galena, sulphur might be manufactured in this country, and advantageously, especially from galena, which is very abundant in the neighbourhood of St. Louis. In the roasting of the ore, all the sulphur is now lost, tons of which might be collected. For the purpose of gunpowder, the purer the sulphur, the better will be the powder; hence attention is always paid to this circumstance. M. Michel, one of the principal refiners of sulphur at Marseilles, has improved the process for purifying sulphur for the purpose of gunpowder. M. Libaw, connected likewise with the French national powder establishment, has furnished a very useful and important memoir on the same subject. Two methods are proposed for the refining of sulphur, which we will briefly state, namely, fusion, and sublimation. The first is conducted in iron pots fixed in a furnace; and the sulphur, before it is thrown in, is beaten into small pieces with a mallet. This facilitates the fusion, and renders it more uniform. Small portions at a time are thrown into the boiler, and stirred frequently with a wooden spatula. This manipulation ought to be continued till the boiler is filled. The heat must be regulated so as not to inflame, or sublime the sulphur.