In the sudden death of Professor Rotch Harvard has lost one of its most valuable and widely known teachers. Although not a graduate of the College, and connected with the University for only six years, he lent during that short period, the fruits of a wide experience and rare knowledge which had combined to win for him an international reputation. By his association with Harvard, the unusual honors conferred by the French and German governments reflected the highest credit on the University which he served. As the founder and director of the Blue Hill Observatory, he added enormously to a formerly meagre knowledge concerning meteorology and climatology. And it is chiefly to him that we owe what advancement has lately been made in the study of the air in relation to aerial navigation. Professor Rotch will long be remembered as a pioneer in that branch of scientific knowledge of which we have so far seen only the beginnings.