The world, which is not apt to believe in ideal motives, calls this feeling love of fame. But there is a decisive criterion by which both kinds of sentiment can be discriminated. Ask the question if it is the same thing to you whether the results of investigation which you have obtained are recognised as belonging to you or not when there are no considerations of external advantage bound up with the answer to this question. The reply to it is easiest in the case of chiefs of laboratories. The teacher must usually furnish the fundamental idea of the research as well as a number of proposals for overcoming experimental difficulties, in which more or less ingenuity comes into play. All this passes as the work of the student, and ultimately appears in his name when the research is finished. Who can afterwards decide what one or the other has done? And how many teachers are there not who in this respect are devoid of any jealousy? Thus, gentlemen, I have been in the happy position that, in freely following my own inclination, I have been led to researches for which you praise me, as having been useful and instructive. I am extremely fortunate that I am praised and honoured by my contemporaries, in so high a degree, for a course of work which is to me the most interesting I could pursue. But my contemporaries have afforded me great and essential help. Apart from the care for my own existence and that of my family, of which they have relieved me, and apart from the external means with which they have provided me, I have found in them a standard of the intellectual capacity of man; and by their sympathy for my work they have evoked in me a vivid conception of the universal mental life of humanity which has enabled me to see the value of my own researches in a higher light. In these circumstances, I can only regard as a free gift the thanks which you desire to accord to me, given unconditionally and without counting on any return. PRINTED BY SPOTTISWOODE AND CO. LTD., NEW STREET SQUARE LONDON WORKS BY JOHN TYNDALL, D.C.L. LL.D. F.R.S. FRAGMENTS of SCIENCE: a Series of Detached Essays, Addresses, and Reviews. 2 vols. crown 8vo. 16_s._ NEW FRAGMENTS. Crown 8vo. 10_s._ 6_d._ LECTURES on SOUND. With Frontispiece of Fog-Syren, and 203 other Woodcuts and Diagrams in the Text. Crown 8vo. 10_s._ 6_d._ HEAT, a MODE of MOTION. With 125 Woodcuts and Diagrams. Crown 8vo. 12_s._ LECTURES on LIGHT, DELIVERED in the UNITED STATES in 1872 and 1873. With Portrait, Lithographic Plate, and 59 Diagrams. Crown 8vo. 5_s._ ESSAYS on the FLOATING MATTER of the AIR in RELATION to PUTREFACTION and INFECTION. With 24 Woodcuts. Crown 8vo. 7_s._ 6_d._ RESEARCHES on DIAMAGNETISM and MAGNE-CRYSTALLIC ACTION; including the Question of Diamagnetic Polarity. Crown 8vo. 12_s._