I submit an estimate of the expense of a glass ceiling, amounting to five thousand dollars. If this plan is adopted by the honorable House of Representatives, the work could be executed in the recess.

Experience, I think, has proved, that the objections to the present Hall are not so forcible as they were last season, but that the members are better heard, as they become accustomed to the room, and to the pitch of voice required ; yet, if it should be considered so inconvenient that the necessity of improving it should be thought indispensable, and would justify the expense, I would recommend that the glass ceiling be built, and a trial made of its utility at the next session.

Respectfully presented by.

Charles Bulfinch.

No decisive measures were taken in consequence of this examination and report, and the evil still being complained of, the Committee on Public Buildings was again directed, at the following session, to consider the subject anew, when the architect presented the following report to the Chairman of the Committee :

Every work on Natural Philosophy, in general, contains observations on acoustics, and endeavors to explain the principles of musical instruments, the vibrations of strings, and the nature and cause of echoes ; but these principles have seldom been applied for useful and practical purposes, to the construction of the interior of large rooms for deliberative assemblies. Places of public worship and theatres have received a greater share of attention, and the result of experience on such apartments, has been to avoid lofty domes, and arched ceilings of great elevation. The manner in which sound operates on the air, has been the subject of much inquiry ; the theory generally adopted, supposes that sound is projected in direct lines, and that it is governed by the same principles as rays of light; and that it is reflected from the substances which it encounters, in angles, equal to the angles of incidence. Another theory supposes that sound is propagated by an undulatory motion of the air, and that resonnances and echoes are produced by the sound being conducted along the surface of intervening walls or other bodies.

The most judicious and practical writer on this subject that I have had the opportunity to consult, is Saunders, on the construction of Theatres. I beg permission to quote from him a few observations. " The supposition of sound being reflected on the same principles as light, has been very generally admitted, and in order to support this theory, it is asserted that sound is propagated in direct rays. Accordingly, Kircher, and most of those who follow him, after explaining the progress of sound to be undulative, go on comparing its properties with those of light: which is clearly refuted by Sir Isaac Newton, who says, ' a pressure on a fluid medium cannot be propagated in right lines, but will be always inflecting and diffusing itself every way, beyond any obstacle that may be presented to it. Sounds are propagated with equal ease, through crooked tubes, and through straight lines ; but light was never known to move in any curve, nor to inflect itself.' The French Encyclopedists, who adopt the theory of the reflection of sound, are obliged to quality it by acknowledging that the theory is still vague and uncertain, and that the comparison of the laws of the reflection of sound with that of light, may be true to a certain point, but it is not without restrictions, because sound is propagated in every direction, and light in right lines only".

Mr. Saunders, after a course of experiments, comes to this conclusion, that sound is affected by vibration among the particles of air, and moves in a circular undulating form. That echo is produced by conduction, and not by reflection, as heretofore imagined. It depends on the conductor, and the nature and form of the substance it meets with. He asserts that, after a smooth surface of water, stone is the most powerful conducter of sound ; experience proves that smooth walls of plaster are next in order, then surfaces of woods, and lastly, hangings of tapestry or woollen cloth.

These observations and results are important, when applied to the Hall of the House of Representatives. The difficulty of hearing and speaking arises, in the first place, from the great size of the room ; and is an evil which must always be apprehended in any room constructed to afford such ample conveniences for so numerous a body, unless the speakers will consent to mount a tribune, situated in the most favorable position : and in the second place, from the resonnances or echoes, occasioned by the dome of 60 feet elevation from the floor. If these echoes could be checked, the difficulty of speaking and hearing would be, in a great measure, removed. For this purpose, I ventured to propose, in 1821, a horizontal ceiling of glass ; but this is liable to objections, from the great difficulty of keeping so large a surface clean, and from the bad effect to be apprehended on the air of the room, from reducing it so much in its dimensions.

Private individuals have no motive for making experiments on the principles of the expansion of sound, and companies of proprietors of buildings are deterred from doing it, by the uncertainty of the effect, and by the expense. An opportunity is at present offered to Congress, to authorize some experiments during the recess, which may be of good consequences, and would, at least, extend a knowledge of the true principles which govern the operations of sound. With this view, I take the liberty to mention the following :

The Grecian and Roman Theatres were constructed without roofs, and were entirely open above ; but it was usual to stretch a covering of sail cloth over the circular seats, to protect the audience from the inclemency of the weather. I would take a hint from this practice, and propose, that cords should be strained, at the springing of the dome, to support a ceiling of light woollen cloth or flannel, projecting ten feet from the columns, within the semicircle. If the theory of conduction of sound be correct, this horizontal projection will prevent it reaching the dome, to occasion the echoes complained of. The experiment might be tried at moderate expense, and, if found effectual, the ceiling might be finished afterwards, in a more permanent manner.