TO THE MANAGERS OF THE ROYAL INSTITUTION.--Count Rumford requested me to arrange and put on paper my ideas concerning the plan and economy of the Royal Institution for the perusal of the managers. On looking over the prospectus, however, I find the plan so well digested that I cannot make any improvement or even advantageous alteration. I shall therefore confine myself in the following observations to what I conceive to belong more particularly to my department--I mean the arrangement of the lectures--and shall propose a plan which, from experience, I think most likely to be useful; but I propose it with the utmost deference to the opinions of the managers, and shall be ready to make any alterations which they may think proper to point out. Our object ought undoubtedly to be both amusement and instruction. We shall have two classes of auditors, the one consisting of those who will come chiefly for amusement or because it may be fashionable. These it is our business to amuse, while at the same time I hope we shall be able to interest them in the subjects, and communicate considerable knowledge without any trouble to themselves. For these I would propose a popular course of experimental philosophy, in which all abstract reasoning shall be avoided, the most entertaining and interesting experiments introduced, and the whole calculated to afford pleasure and instruction to those who have not had an opportunity of examining these subjects and to refresh the memory of those who have. On the supposition that the lectures of the Institution should open the first week in February, if we appropriate one evening a week to it, we can comprise this course in eighteen or twenty lectures, each lecture to continue only an hour, that the attention may not be fatigued. A course of lectures on chemistry, popular and amusing, at the same time sufficiently scientific, might be given twice a week. This course would contain the elements of chemistry and the application of this science to the arts and manufactures, and would be illustrated by interesting and pleasing experiments. For the sake of the second class of auditors, which would not at first be the most numerous, but which would continually increase in number, even though the auditors of the other course should diminish--I mean those attached to scientific pursuits--I would propose a full and scientific course of experimental philosophy on the plan generally adopted in universities. In this course particular attention should be paid to mechanics, hydrostatics, hydraulics, and pneumatics, which are the most useful branches of mechanical philosophy. The mathematical demonstration of the propositions would first be given, next the experimental proof, and lastly the application of each to the mechanical and chemical arts.