IT was with great regret that I saw the announcement of the death in New York on April 17 of Prof. Jean Perrin. He had many friends in England who will feel that we have lost a staunch ally, for it will be remembered that during the War of 1914–18 he was of the greatest assistance to every one engaged in scientific work for the Government departments. He was himself scientific adviser to the French Government, and was keenly interested not only in what was being done in Paris but also in the work done in England, especially the development of tanks. He disliked the Germans very much, and during the whole of the period 1914–18 and shortly before this War broke out the spirit that animated him was “II faut écraser les Boches”. It was some consolation to know that he and his son had got out of Occupied France and gone to the United States.