In those days the name of Kirchoff was coupled always with that of an associate, the chemist Bunsen, when there was mention of spectrum-analysis; and in my time at Heidelberg, Bunsen was at hand and I became as familiar with his figure as with Kirchoff. In frame Bunsen was of the burly burgomaster type not rare among the Teutons, and as I saw him in his laboratory to which I sometimes gained access through students of his, he moved about in some kind of informal _schlafrock_ or working dress of ample dimensions, with his large head crowned by a peculiar cap. On the tables within the spaces flickered numerously the "Bunsen burners," his invention, and it was easy to fancy as one saw him, surrounded by the large company of reverent disciples, that you were in the presence of the hierophant of some abstruse and mysterious cult, in whose honour waved the many lambent flames. I think he was unmarried, without domestic ties, and lived almost night and day among his crucibles and retorts, devoted to his science and pupils toward whom he showed a regard almost fatherly. In his lecture-room, in more formal dress he was less picturesque, but still a man to arouse deep interest. He was in the front rank of the chemists of all time, and I suppose had equal merit with Kirchoff in the momentous discovery in which their names are linked. There was, however, at this time in Heidelberg a scientist probably of greater prestige than even these, whose contemporary influence was more dominant, and whose repute is now, and likely to be hereafter more prevailing. In my walks in a certain quiet street, I sometimes met a man who made an unusual impression of dignity and power. He had the bearing of a leader of men in whatever sphere he might move, massive and well-statured, his dress not obtrusive but carefully appointed, with an eye and face to command. His manner was courteous, not domineering, and I wondered who the able, high-bred gentleman might be, for he carried all that in his air as he passed along the street. It was the illustrious Helmholtz, then in his best years, with great achievements behind him and before. His researches in many fields were profound and far extending. I suppose his genius was at its best when dealing with the pervasive imponderable ether that extends out from the earth into the vast planetary spaces in whose vibrations are conditioned the phenomena of light. No subject of investigation can be more elusive. The mind that could grapple with this and arrive at the secrets and laws of the subtle medium through which the human eye receives impression is indeed worthy of our veneration. Probably, excepting Humboldt, no German scientist in these later centuries has reached such eminence. The fields of the two men were widely different. The one we know best as the scientific traveller, roaming the earth over, and reducing to ordered knowledge what can be perceived of its fauna and flora, of the strata that