I am, Sir, Your obedient servant, THOMAS YOUNG, M.D., Sec. Bd. Long. Michael Faraday, Esq., Royal Institution. In February, 1825, Faraday’s duties towards the Royal Institution were somewhat modified. Hitherto he had been nominally a mere assistant to Davy and Brande, though he had occasionally undertaken lectures for the latter. Now, on Davy’s recommendation, he was, as we have seen, appointed by the managers Director of the Laboratory under the superintendence of the Professor of Chemistry. He was relieved, “because of his occupation in research,” from his duty as chemical assistant at the lectures. The research on optical glass was not concluded till 1829, when its results were communicated to the Royal Society in the Bakerian lecture of that year--a memoir so long that it is said three sittings were occupied in its delivery. It is printed _in extenso_ in the _Philosophical Transactions_ of 1830. It opens as follows:-- When the philosopher desires to apply glass in the construction of perfect instruments, and especially the achromatic telescope, its manufacture is found liable to imperfections so important and so difficult to avoid, that science is frequently stopped in her progress by them--a fact fully proved by the circumstance that Mr. Dollond, one of our first opticians, has not been able to obtain a disc of flint glass 4½ inches in diameter, fit for a telescope, within the last five years; or a similar disc, of 5 inches, within the last ten years. This led to the appointment by Sir H. Davy of the Royal Society Committee, and the Government removed the excise restrictions, and undertook to bear all the expenses as long as the investigation offered a reasonable hope of success. The experiments were begun at the Falcon Glass Works, three miles from the Royal Institution, and continued there in 1825, 1826, and to Sept., 1827, when a room was built at the Institution. At first the inquiry was pursued principally as related to flint and crown glass; but in September, 1828, it was directed exclusively to the preparation and perfection of peculiar heavy and fusible glasses, from which time continued progress has been made. In 1830 the experiments on glass-making were stopped. In 1831 the Committee for the Improvement of Glass for Optical Purposes reported to the Royal Society Council that the telescope made with Mr. Faraday’s glass had been examined by Captain Kater and Mr. Pond. “It bears as great a power as can reasonably be expected, and is very achromatic. The Committee therefore recommend that Mr. Faraday be requested to make a perfect piece of glass of the largest size that his present apparatus will admit, and also to teach some person to manufacture the glass for general sale.”