Portrait of Lord Kelvin, taken in 1895, facing page 127 of "Reflections on the Motive Power of Heat", second edition, 1897. See page xiii - Note to Second Edition. The present edition of this little work is improved by the removal of a few errata observed in the first issue, and by the addition of a recent and excellent portrait of Lord Kelvin, as a frontispiece to his era-making paper, at page 127. This picture, taken within the last year, is thought by the friends of its distinguished subject to be one of the best yet produced. That it is satisfactory to him and his friends is indicated by the fact that the original of this reproduction was presented to the writer by Lady Kelvin, in 1895, immediately after it was taken, and the autograph supplied by her distinguished husband.