Bulletin 91 of the Bureau of Chemistry, United States Department of Agriculture, relates to a recent chemical investigation of American commercial mineral waters. The waters examined by the government chemists are all found in the markets of the country and are recommended to the public in virtue of certain valuable mineral ingredients they are stated to contain, or on the score of their purity and freedom from harmful substances. Included in the analyses are many of the best known springs of the United States, some of which have long held a high place in the estimation of physicians. It is proper, therefore, that the results be given wide publicity and the essential facts reviewed. Ranged in contrast with their own tables the bureau chemists present the analyses of the waters as hitherto advertised by the owners or managers of the springs, and upon which the medical men of the country