The cost of producing oxygen at Westminster, under specially expensive conditions, is high--about 12s. per 1,000 cub. ft. When we consider, however, that the cost should only embrace attendance, fuel, wear and tear, and a little lime and soda for the purifiers, that the consumption of fuel is small, the wear and tear light, and that the raw material--air--is obtained for nothing, it ought to be possible to produce the gas for a third or fourth of this amount in most of our great manufacturing centers, where the price of fuel is but a third of that demanded in London, and where provision could be made for economizing the waste heat, which is entirely lost in the Westminster installation. Moreover, in estimating this cost all the charges are thrown on the oxygen; were there any means of utilizing the 4,000 cub. ft. of nitrogen at present blown away as waste for every thousand cubic feet of oxygen produced, the nitrogen would of course bear its share of the cost. The question of the application of the oxygen is one which must be determined in its manifold bearings mainly by the experiments of chemists and scientific men engaged in industrial work. Having ascertained the method by which and the limit of cost within which it is possible to use oxygen in their work, it can be seen whether by Brin's process the gas can be obtained within that limit. Mr. S.R. Ogden, the manager of the corporation gasworks at Blackburn, has already made interesting experiments on the application of oxygen in the manufacture of illuminating gas. In order to purify coal gas from compounds of sulphur, it is passed through purifiers charged with layers of oxide of iron. When the oxide of iron has absorbed as much sulphur as it can combine with, it is described as "foul." It is then discharged and spread out in the open air, when, under the influence of the atmospheric oxygen, it is rapidly decomposed, the sulphur is separated out in the free state, and oxide of iron is reformed ready for use again in the purifiers. This process is called revivification, and it is repeated until the accumulation of sulphur in the oxide is so great (45 to 55 per cent.) that it can be profitably sold to the vitriol maker. Hawkins discovered that by introducing about 3 per cent. of air into the gas before passing it through the purifiers, the oxygen of the air introduced set free the sulphur from the iron as fast as it was absorbed. Thus the process of revivification could be carried on in the purifiers themselves simultaneously with the absorption of the sulphur impurities in the gas.