And not only is the building worthy a visit on account of the many interesting relics it contains of some of our greatest scientists, and on account of the memoirs of its many great men, but even to the unscientific there is much that is attractive in the Friday Evening Lectures, which since that year 1826, when Faraday may be said to have inaugurated them, up to now, have been regularly carried on. No trouble is spared by the lecturers to make their matter understood, and innumerable experiments are presented on these occasions. The experiments, too, are such as often require a great expenditure of time and trouble in their preparation. As an instance of this I may mention an experiment which was made on the occasion of my latest attendance at a "Friday evening." The lecturer was Professor Harold Dixon; the subject of which he was treating was "The Rate of Explosion of Gases." To show the rapidity with which an explosion of a certain gas travelled, the lecturer had fitted up a leaden piping all round the theatre; the ends of the piping rested upon either end of the table at which Professor Dixon was lecturing. The piping was filled with gas, and the Professor applied a light at one end; a sharp explosion took place as the gas was fired, and was followed _almost instantaneously_ by an explosion at the other end of the pipe--the explosion having in that very short time travelled through a length of two hundred and twenty feet of piping! I quote this instance to show that no trouble is spared in preparing an illustrative experiment, although such experiment may be demonstrated in a minute or less. It may be appropriate, while considering the long connection of Faraday with the scene of his many experimental triumphs, to refer more particularly to that unique meeting which took place last summer (June 8th, 1891) in celebration of the hundredth anniversary of the birth of Faraday, and to which slight reference is made in the last chapter. The meeting, appropriately enough, took the form of a gathering in the theatre of the Royal Institution of many of the most able and distinguished chemists of the day; Lord Rayleigh delivering an address on the developments of Faraday's discoveries. The chair was taken by His Royal Highness the Prince of Wales, who referred in his opening remarks to the time when he had sat in that theatre and listened to Faraday himself. The letter from H.R.H., which is quoted on p. 131, was read, as was also the following letter which the Prince wrote to Mrs. Faraday on the occasion of her husband's death. "Wiesbaden, September 10, 1867.