SPECIAL ARTICLES.—On relation between rainfall and stream flow [with list of literature cited]; by Richmond T. Zoch.—Snow survey as index to summer precipitation; by O. W. Monson.—Turbidity and water vapor determinations from solar radiation measurements at Blue Hill, and relations to air-mass types; by Herbert H. Kimball.— Estimating yield of grain from weather; by A. H. Bogue.—Time limits of day as affecting records of minimum temperature; by E. S. Nichols.