pain of conflict and the debility of indecision.’ Such was my precise condition in the Alps this year; in a score of words Mr. Bain has here sketched my mental diagnosis; and it was under these evil circumstances that I had to equip myself for the hour and the ordeal that are now come. Gladly, however, as I should have seen this duty in other hands, I could by no means shrink from it. Disloyalty would have been worse than failure. In some fashion or other--feebly or strongly, meanly or manfully, on the higher levels of thought, or on the flats of common-place,--the task had to be accomplished. I looked in various directions for help and furtherance; but without me for a time I saw only ‘antres vast,’ and within me ‘deserts idle.’ My case resembled that of a sick doctor who had forgotten his art and sorely needed the prescription of a friend. Mr. Bain wrote one for me. He said, ‘Your present knowledge must forge the links of connection between what has been already achieved and what is now required.’[2] In these words he admonished me to review the past and recover from it the broken ends of former investigations. I tried to do so. Previous to going to Switzerland I had been thinking much of light and heat, of magnetism and electricity, of organic germs, atoms, molecules, spontaneous generation, comets, and skies. With one or another of these I now sought to re-form an alliance, and finally succeeded in establishing a kind of cohesion between thought and Light. The wish grew within me to trace, and to enable you to trace, some of the more occult operations of this agent. I wished, if possible, to take you behind the drop-scene of the senses, and to show you the hidden mechanism of optical action. For I take it to be well worth the while of the scientific teacher to take some pains, and even great pains, to make those whom he addresses copartners of his thoughts. To clear his own mind in the first place from all haze and vagueness, and then to project into language which shall leave no mistake as to his meaning--which shall leave even his errors naked--the definite ideas he has shaped. A great deal is, I think, possible to scientific exposition conducted in this way. It is possible, I believe, even before an audience like the present, to uncover to some extent the unseen things of nature; and thus to give, not only to professed students, but to others with the necessary bias, industry, and capacity, an intelligent interest in the operations of science. Time and labour are necessary to this result, but science is the gainer from the public sympathy thus created.