health—which was something different from the malady of self-righteousness. I concentrated my chief attention upon mathematics, physics, and chemistry. To the illustrious chemist Bunsen I am specially indebted. He was a man of fine presence, tall, handsome, courteous, and without a trace of affectation or pedantry. He merged himself in his subject; his exposition was lucid, and his language pure; he spoke with the clear Hanoverian accent which is so pleasant to English ears. He was every inch a gentleman. After some experience of my own, I still look back on Bunsen as the nearest approach to my ideal of a university teacher. Professor Stegmann gave me the subject of my dissertation when I took my degree. Its title in English was, "On a Screw Surface with Inclined Generatrix, and on the Conditions of Equilibrium on such Surfaces." I resolved that if I could not, without the slightest aid, accomplish the work from beginning to end, it should not be accomplished at all. Wandering among the pinewoods, and pondering the subject, I became more and more master of it; and when my dissertation was handed in to the Philosophical Faculty it did not contain a thought that was not my own. Continuing to work strenuously but happily till the autumn of 1850, I then came to England. But I soon returned to Germany. To those Marburg days I look back with warm affection, both in regard to nature and to man. To Berlin I went in the beginning of 1851. Magnus, Dove, Mitscherlich, Heinrich and Gustav Rose, Ehrenberg, Riess, Du Bois-Reymond, and Clausius were the scientific stars of the university at that time. From all these eminent men I received every mark of kindness, and formed with some of them enduring friendships. Helmholtz was at this time in Königsberg. He had written his renowned essay on the "Conservation of Energy." In his own house I had the honor of an interview with Humboldt. He rallied me on having contracted the habit of smoking in Germany, his knowledge on this head being derived from my little paper on a water-jet, where the noise produced by the rupture of a film between the wet lips of a smoker is referred to. He gave me various messages to Faraday, declaring his belief that he (Faraday) had referred the annual and diurnal variation of the declination of the magnetic needle to their true cause—the variation of the magnetic condition of the oxygen of the atmosphere. I was interested to learn from Humboldt himself that, though so large a portion of his life had been spent in France, he never published a French essay without having it first revised by a Frenchman. In those days I not unfrequently found it necessary to subject myself to a process which I called depolarization. My brain, intent on its subjects, used to acquire a set, resembling the rigid polarity of a steel magnet. It lost the pliancy needful for free conversation, and to recover this I used to walk occasionally to Charlottenburg or elsewhere. From my experiences at that time I derived the notion that hard thinking and fleet talking do not run together.
