"Dear Sir,--I write to thank you very much for the pleasure you have given me by your lectures, and I cannot help hoping they will not be the last I shall hear from you. Their subject was very interesting, and your clear explanations made it doubly so. "Believe me, dear Sir, yours truly, "ALFRED." It is interesting to learn Faraday's own views with regard to popular lectures, for never yet was there a truly scientific lecturer who was more truly popular; perhaps, indeed, there is no other single man who, without in any degree lowering his work for the purpose, succeeded so well in popularising scientific knowledge. These are his own words on the subject: "As to popular lectures (which at the same time are to be _respectable_ and _sound_) none are more difficult to find. Lectures which _really teach_ will never be popular; lectures which are popular will never _really teach_." His own success as a lecturer was owing largely to the power he had of adapting himself to all minds, from the deepest thinkers to the liveliest youth; this power gave him a "wide range of influence, and his sympathy with the young among his listeners imparted more life and colour to his discourses than they might otherwise have possessed. He had the art of making philosophy charming, and this was due in no little measure to the fact that to grey-headed wisdom, he united wonderful juvenility of spirit." "He was," to quote once more from Lady Pollock's recollections of the illustrious lecturer, "completely master of the situation; he had his audience at his command, as he had himself and all his belongings; he had nothing to fret him, and he could give his eloquence full sway. It was an irresistible eloquence, which compelled attention and insisted upon sympathy. It waked the young from their visions and the old from their dreams. There was a gleaming in his eye which no painter could copy, and which no poet could describe.... His enthusiasm sometimes carried him to the point of ecstasy when he expatiated on the beauty of nature, and when he lifted the veil from her deep mysteries. His body then took motion from his mind; his hair streamed out from his head, his hands were full of nervous action, his light, lithe body seemed to quiver with its eager life. His audience took fire with him, and every face was flushed.... A pleasant vein of humour accompanied his ardent imagination, and occasionally, not too often, relieved the tension of thought imposed upon his pupils. He would play with his subject now and then, but very delicately; his sport was only just enough to enliven the effort of attention. He never suffered an experiment to allure him away from his theme. Every touch of his hand was a true illustration of his argument." As he once remarked in giving advice to a young lecturer: "If I said to my audience, 'This stone will fall to the