It is perhaps idle to speculate why Roscoe should have left Williamson at the most fruitful period of his career, and when, under his stimulus, organic chemistry was apparently about to enter upon a great development in this country. But the probability is that then, as afterwards, the problems of organic chemistry and the purely speculative aspects of the science had few attractions for him, and that he saw in the many-sided nature of Bunsen’s work, in its eminently practical character, and the precision of its quantitative methods, much that appealed to his inclination towards the operative, and especially the determinative side of chemistry, for Bunsen was pre-eminently a master of manipulation, as every one who aspired to a professional career in chemistry and who hoped to direct a chemical laboratory fully recognized. Roscoe, with his mother and sister, who elected to keep house for him, reached Heidelberg in the autumn of 1853 with an introduction to von Mohl, the Professor of International Law, with whose family they became well acquainted. One of the daughters, Anna von Mohl, was the second wife of Helmholtz. By von Mohl he was made known to Bunsen. I shall never forget (says Roscoe in his Autobiography) my first sight of him—the man who afterwards became one of my dearest friends, and to whom I owe more than I can tell.… He was then at the height of his mental and physical powers. He stood fully six feet high, his manner was simple yet dignified, and his expression one of rare intelligence and great kindness. This first impression of his bearing and character only became stronger as my knowledge of him increased, and the feelings of respect and affection with which I regarded him were those of all with whom he came in contact. His singular amiability was not a sign of weakness, but of strength of character. His modesty was natural and in no degree assumed. In his lectures, when giving an account of some discovery he had made, or some new apparatus or method of work which he had investigated, I never heard him mention himself. It was always “man hat dies gefunden,” or “es hat sich so herausgestellt.”