superseding emery and diamond dust as an abradant. It is produced by Acheson (Pat. No. 492,767, Feb. 28, 1893), by passing a current of electricity through a mixture of silica and carbon. _Calcium carbide_, a rare compound a few years ago, is now cheaply produced by the action of an electric arc on a mixture of lime and carbon, as described by Willson (Pats. Nos. 541,137, 541,138, June 18, 1895). Calcium carbide resembles coke in general appearance, and it is used for the manufacture of acetylene gas, for which purpose it is only necessary to immerse the calcium carbide in water, and the gas is at once given off by the mutual decomposition of the water and the carbide. _Agricultural chemistry_ is another one of the practical developments of the Nineteenth Century. A hundred years ago the farmer planted his crops, prayed for rain, and trusted to Providence for the increase; he was not infrequently disappointed, but was wholly unable to account for the failure. To-day the intelligent farmer understands the value of nitrogen, has ascertained how it may be fed to his crops through the agency of nitrifying organisms, or he has his soil analyzed at the Agricultural Department, finds out what element it lacks for the crop desired, and in chemically prepared fertilizers supplies that deficiency. The chemical analysis of drinking water has also contributed much to the knowledge of right living and to the avoidance of disease and death, which our forefathers were accustomed to regard as dispensations of Providence.