Under a cooperative agreement between the Bureau of Mines, the United States Geological Survey, and the United States Bureau of Standards, a study of the stone-quarrying industries of the coun try was begun in 1914. The results of investigations made have been published from time to time.1 During the World War the Bureau of Mines centered its attention on problems relating to national de tense, and detailed studies of stone-quarry problems were not under taken except for an investigation of labor saving at limestone quar ries, reported in Technical Paper 203, which related to a question of military importance. Since the return of peace, the high cost of materials and labor has made more imperative than in prewar times the conduct of investigations for aiding the quarrying industries in every way possible to adopt more economical methods and to utilize the most efficient labor-saving equipment. The publications already issued have had a wide demand, and in the interest of the quarry industries the bureau proposes to issue additions to the series as rapidly as funds are available. In an endeavor to promote economy and the reduction of waste in the slate industry, a study of slate quarrying was begun in 1920 and covered a period of about two years. Sixty-five active quarries were visited, and a detailed study made of all problems bearing on their successful operation. Field study was supplemented by a study of all information available in books or published articles on slate quarrying.