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ACOUSTICS APPLIED TO THE HOUSES OF PARLIAMENT.

and invert the last result for the required fraction.

Taking the given number 3488372 + as before, by continual division we obtain the quotients 2, 1, 6, 1, 1, and by the second part of the rule :

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and the fractions.

92

33

69

2 3 11 14 39 53 1 1'4' 5' 14' 19'

Inverted=

33
92'

the equivalent

vulgar fraction; and the equivalent decimal is, 358695652173913043478260.

Were it possible to ascertain at first that the given number is part of a pure circulate, the rule given by Mr. Peacock is much shorter, and more convenient; but, as there are no means of determining it to be pure until the whole of the series is ascertained, it will be necessary to treat it as mixed, and use the foregoing rule. There may possibly be other methods of determining this question; and if so, I should be glad to see your valuable Magazine the medium of communication on this interesting subject, agreeing as I do with Mr. Peacock, that if the attentions of a few minds were directed to it, it would lead to most important results. I remain, Sir, your obedient servant, G. C. L. Kentish Town, April 24, 1836.

P. S.-If the rule be not perfectly intelligible, I shall be very happy to give the process in full, or any required explanation.

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Having thus shown the applicability of the rule to pure circulates, I will now apply it to the mixed circulate 3586956 +.

By continual division, as before, we obtain the quotients, 2, 1, 3, 1, 2, 1, 1;

ACOUSTICS APPLIED TO THE HOUSES OF
PARLIAMENT.
(Extracts from the Evidence of Dr. Reid before the
Select Committee on the Ventilation of the Houses
of Parliament.)

Have you directed your attention to the communication of sound in public buildings? -Accidental circumstances have led me to pay considerable attention to that subject, of late.

You constructed on some scientific principles the room in which the great dinner was given to Earl Grey in Edinburgh ?—I was on the committee on that subject, and many of the members of the committee, along with the architect, were frequently in my classroom; but I cannot take the credit of having constructed it. I believe I gave what hints I could with respect to the form and several other circumstances connected with the sound; but the merit of the arrangements is due to the architect, Mr. Hamilton.

You were aware of all the principles on which it was constructed?—Yes; but I dif fered with respect to the use of the canvass; I was anxious to increase its power in communicating sound at the expense of some ornament which could not be introduced well without the canvass, though even with the

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ACOUSTICS APPLIED TO THE HOUSES OF PARLIAMENT.

canvass I believe there was no room in which communication of sound was heard with greater advantage under the circumstances. Perhaps I may be allowed to mention that I tried the room with the canvass, and after the canvass had been taken down, and that, in order to be capable of forming a most decided opinion on the subject from actual trial, I employed people to read and to sing in it, that I might study its power of communicating sound in every possible manner; and thinking it a most excellent opportunity of also trying the comparative power of the canvass and the wood, though I believe people are generally agreed on that subject, I consulted Hertz, the piano-forte player, and also Mr. Murray and Mr. Findlay Dunn, celebrated for their professional talents and attainments in those experiments, and Hertz mentioned particularly, “that the sound was not sonorous," that was his expression. It was beautifully distinct and clear; I am not aware that in any room music was ever heard which was so beautifully clear and so melodious; but at the same time it had not that strength and power which was observed when the canvass was pulled down, and when the sound was strengthened by a reflection from the roof. The beauty of music upon a lake or other still-water is proverbial, and I attribute it to the same cause, to the purity of the tone where there are no prolonged reverberations interrupting each succeeding note.

What should you consider the essential conditions of a room for the purpose of the Houses of Parliament in reference to the communication of sound?-With respect to the form, a square form on the whole I should be inclined to prefer, as bringing the Members nearer to one another than can be done in any other way.

.Than by a circle?—I was going to add, than by the circular form, which is very ill adapted for the communication of sound in a building such as the House of Commons, whereas the other is not.

Do you mean perfectly square, or oblong? -I would say about square. Again, the walls ought to be as low as possible, and -arranged in such a manner that no sound can be reflected repeatedly from the one to the other. The roof ought to be as low as possible, or as low as may be consistent with the size of the building, and to have a great reflecting power, so that the direct voice of the speaker may be strengthened by the reflection from the roof; and, lastly, the voice having been strengthened by this single reflection, all further continuance of the sound ought to be destroyed by throwing it upon some absorbing surface, as upon an irregularly and matted floor. I might add here, from a number of different experiments, I

found no difficulty in conversing at the dis-
tance of from 100 to 1,000 feet in the open
air. Sir John Ross told me lately, when I
met him at Dublin, that he had no difficulty
in conversing at the distance of a mile in the
still and silent atmosphere, which often oc-
curs in the polar region. Lieutenant Bowen
has conversed at the distance of a mile, or
upwards, across a frozen lake, and Mr.
Parkin, of the Royal Marine Hospital, Wool-
wich, informed me, among many other in-
teresting circumstances, that at a particular
place near the top of the hill at Cawsand
Bay, he had frequently heard with the ut
most distinctness the laugh and conversation
of the sailors on board of the frigates and
other vessels at anchor there, one to two
miles distant from the place where he was.
The difficulty of the communication of sound
in public buildings, therefore, must be at-
tributed, in most cases at least, not so much
to a want of power in the voice of the speaker
as to the interruptions which arise from pro-
longed reverberation and other causes.
some rooms, after ceasing to speak, I have
found the sound continued for five seconds,
and I have no doubt that it was continued for
a much longer time, though we could not
directly affirm that we heard a distinct tone.
Every instant that sound is continued, after
once a new sound shall have fallen upon the
ear, tends to make it less and less distinct.

In

As to the distance at which it is stated sound is heard in high latitudes, do you attribute that principally to the perfect silence of the atmosphere, a total want of all agitations, or a peculiar state of atmosphere itself! I should be inclined, from what I have heard myself, and trying the communications of sound in all situations, to attribute it principally, if not entirely, to the extreme stillness of the atmosphere. When the wind flows gently in any particular direction, it favours the communication of sound considerably in the same path. know an instance where the sound of a powerful military band was heard, though imperfectly, at the distance of twenty miles. The noise of a steam-boat, or even of oars of a small boat, are easily heard, under favourable circumstances, at a distance of many miles.

I

Your general principle is, in reference to the House of Commons, that there should be one reflecting surface extending as nearly as possible over the Members by the ceiling, that the walls should be non-reflecting, and the floor absorbing, to prevent the echo; but you do not state the form of the ceiling, whether it is to be coved or flat?-The form of the ceiling is that which you see represented in the sketch of my class-room; it should be inclined and meet in a point.

Do you recommend that form of ceiling with reference to its superiority for ventila

„ACOUSTICS APPLIED TO: THE HOUSES OF. PARLIAMENT.

tion or hearing? On account of both these; I think it frequently happens that both circumstances combine; the same form of ceiling that allows all the moist heated air in a crowded evening to collect at the top, will also throw most broadly the pulses of sound across the greater portion of the audience, the object being, not that the sound should accumulate in any particular part, but be diffused as equally as possible over the whole of the House. If you have a broad reflecting surface, inclined in that manner, it may be shown that that surface is most conducive, and will be most powerful, in distributing the pulses of sound equally among the Members.

>But in that form the person speaking from near the wall would be better heard than if The were speaking in the centre?-That may be; but it seems that in every part of a room constructed on that principle, whether the -person speaking be in sight or out of sight, whether one or two be in the room, or several Thundreds, there is no difficulty either in hearing or in distinctness of articulation. Many rooms will produce a more loud and sounding noise, perhaps they will be better for the premier coup d'orchestre in a concert room, but if it is distinctness of articulation that is wanted, or to experience melody in its purest form, strengthened however by a certain reflection from the roof, that is the form I would recommend. The difference between distinctness and purity of intonation, however low the tone may be, and that confused and noisy sound that is pro-duced in some rooms, has been very little attended to, practically, in the construction of buildings, and still less the effect of reflection upon the voice of the person speaking. Where, from any particular cause, many reflected sounds strike upon his mouth, it is impossible for him to articulate distinctly, however articulate, under other circumstances, his enunciation may be; a physical cause opposes the free action of the muscles that regulate those movements by which speech is produced, and any one who studies the subject practically, till experience makes him familiar with it, will acknowledge the great difference in the sensation produced upon the mouth when he speaks in a well-constructed room and then in the focus of a large parabolic reflector, for example, ópposed to a powerfully reflecting wall.

Of what material would you propose to construct an interior?-I would propose that it should be constructed of wood, and that it should, as far as possible, resemble the sounding-board of a piano-forte. In experi"ments in the open air, when we were in a valley, and the situation peculiar, I have repeatedly spoken to individuals 200 feet distance from me when they did not hear a word,

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if they were in the line of the valley, so that there was a great hollow extending indefinitely behind them; while others who were still more distant than them, at twice or three times the distance, but who happened to be at one of the sides, heard distinctly every word without the slightest effort.

Then they heard reflected sound?-They heard the primary united with the reflected sound; they were so close to the reflecting surface, the primary sound no sooner came to them than the reflecting sound came up and strengthened the primary impression; so in the same manner the roof should be so near the Members that the voice of the person speaking should be strengthened by the reflection. If we admit a certain height for ornament and ventilation, let that be as low -as possible, and the more equal will be the communication of sound in my opinion, not only from theory, but from direct experiment in my own class-room and other buildings.

It seems to follow, from what you have said, that you would recommend the Houses of Parliament to be without galleries?-I should strongly recommend they should be without a projecting gallery; but a retreating gallery would not be very disadvantage

ous.

With reference to the position of the Speaker of the House of Commons, would you propose to adapt what is called the Speaker's chair to the favourable transmission of sound, or trust entirely to the room itself? I should have no hesitation in saying I would trust entirely to the room itself, were it constructed on these principles. At the same time, if it was fixed that the Speaker's chair should have a place near the wall, which I presume may very probably be the case, it would be almost unnecessary to do any thing for the communication of the sound, as, if that were made a good reflecting surface, and inclined in such a manner that no reflection were kept up between wall and wall, he would require no peculiar arrangement either to hear or to be heard, without any effort, in any part of the room.

In that case the Speaker would always be directing his voice, in point of fact, towards an absorbing surface, for the strangers' gallety must be opposite to him, and not in the side of the roof?-He would, under those circumstances; but at the same time the sound would be reflected from the roof, spreading from the situation in which he was placed on either side the roof, inclining on either side of the Speaker.

Would you explain upon what principle you have a preference for a square to a circular form?-On this principle: whenever there are any concave surfaces, it is the same, generally speaking, with sound as with light; that is, from the angle which the sound

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ACOUSTICS APPLIED TO THE HOUSES OF PARLIAMENT.

makes as it falls upon the surface, it is necessarily collected into foci, and in circular rooms there are, accordingly, more or less points where the sound is heard with greater power, while it is comparatively deficient in other places. The object in the House of Commons being an equal transmission of sound, that is the reason why I give a preference to a flat surface.

If you were understood rightly, you would depend principally on the ceiling for the reflection of the sound, and you propose to have walls of an absorbing surface?-The part of the walls that are brought more immediately into play would be so extremely low, and converted at the same time into a kind of gallery, that perhaps, with the exception of that part where the Speaker may be placed, they could scarcely be said to have any of the properties of ordinary walls in reflecting sound.

By adopting the circular form, you would bring the Members closer together, and therefore in that point of view they will be able to make each other heard more easily?—I am not aware that the advantage gained in this respect would in any way balance the difficulties that would present themselves from the collection of sound in foci; and even, whatever materials are used, it is perhaps - impossible to have a surface that is absolutely non-reflecting; it is more or less reflecting merely in comparison, for even the very canvas we at times put up to destroy the reflecting power which may predominate in some particular buildings, has been known in other cases, when stretched, as in the sails of a ship, to collect pulses of sound from bells that have been ringing 100 miles distant, and rendering them observable.

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As to the position of the seats, have you any idea whether it is convenient or no for the transmission of the sound that they should be raised one above another?-As the floor is considered to be an absorbing surface, on the principles I have alluded to, should imagine that if they were elevated one above another, so as to allow the Speaker to see the Members distinctly, and the Members to see one another, it would rather facilitate the communication of sound, and the perfect absorption of the reflected sound.

In fact, the elevation of the back seats would tend to diminish practically, so far as sound went, the height of the walls?—Yes.

And to diminish the inconvenience of the circular form?-Yes; at the same time it being admitted that the power of sound is proportional to the intensity of the mechanical impulse made, the area through which is to diffuse itself, and the manner in which it is strengthened by the reflection from the walls, every space, every superfluous space, that can be cut off without interfering with

the principles above alluded to, or rather with their applications, will be a gain to the Members in facilitating the communication of sound.

As to the openings in the roof and walls for light and air, should you propose to arrange them according to any past experience you have had?-I should consider that an object of very great importance. The first thing that led me to direct my attention to this subject was what occurred in a church, where it was almost impossible to hear the preacher, in consequence of the prolonged reverberation. After spending some little time in it I left it, and was surprised, when I was totally out of sight of the preacher, to find that I heard every word distinctly. On examining into the circumstance, I could only attribute it to this cause, viz. that the direct voice of the speaker was perfectly sufficient to be audible in every part of the building, but that, at those particular openings into the passage, it alone had come out, and there affected my ear alone, whereas, in the interior of the building, I not only heard the direct voice of the speaker, but also the confused noise produced by all the prolonged reverberation of preceding words. If, then, from one or two apertures alone such a body of sound can escape as will render the speaker's voice distinctly audible in separate apartments, we are entitled to infer, that if that portion be prevented from escaping, it would tend much to add to the power of the speaker's voice within the House. Further, not only will the loss of sound be prevented, but also the entrance of all discordant sounds from without. In every large city there is a continual hum, and the noise of people walking in the street, of bells, of horses, of coaches, and the like, though on every occasion they may not be distinctly audible, still produce a certain amount of sound, which detracts from the purity of intonation. If, then, the loss be prevented on the one hand, and the entrance of discordant sounds on the other, there will be much added to the power of the room in communicating sound. In those rooms where I have seen all those openings arranged in such a manner, that while air was permitted freely to enter or to escape, yet the sound had to be reflected two or three times in passages, so that it was lost as it were, and could not produce any specific effect if entering from without, or reflected back into the room if formed within, the intonation was more powerful and more distinct than when that was not attended to.

Is the glass of windows equally efficacious, in your view, of sound as wood?—Yes.

Would you state to the Committee whether you consider glass as eligible for the reflection of sound as wood?—I should certainly consider it so in those situations.

ACOUSTICS APPLIED TO THE HOUSES OF PARLIAMENT.

As to the outward walls, what sort of thickness do you think they should be with regard to the sound; ought there to be a very thick outer wall or not?-I should prefer a thick outer wall, as giving more power to heating in winter and of cooling in summer, as well as in reference to the communication of sound.

And in excluding sound?—Yes; a thick wall would render it freer from all disturbing causes, whether from sound or cold.

Do you contemplate the actual roof of the House of Commons should also be the outer roof, or a double roof?-I should contemplate a double roof; for in case of noise from rain or hail, if there were only one roof, it would be almost impossible to prevent the greatest interruption, and in summer no means could be adopted with facility to prevent the room becoming extremely warm.

Would you rigidly interdict the use of all ornamental work in such a roof?-On no account; I should consider it not merely desirable for its own sake, but advantageous for sound. Had it not been necessary to attend in the strictest manner to economy in a large establishment I put up at my own expense alone, I should have had every one of these cross partitions in the roof ornamented. I consider these cross partitions are of great value in respect to the communication of sound, and on this ground: in the first place, experimentally, I found that if I made an impulse in water in a particular direction, instead of that impulse extending, as it were, throughout the whole of the water, as it is generally believed to do, a wave was made to roll along upon a particular surface, while the rest of the water was quiet and still; this I believe to take place to a certain extent in the communication of sound; if the voice, for instance be directed on an extremely plain surface, at a particular angle we know we can speak to people at a great distance, if we both go nearer the side of a wall; now if so much of the sound were to fall on the roof at this particular angle, my opinion is, it would run along the roof a considerable way before any amount of it would be reflected on the ground; whereas if the surface of the roof be broken by transverse beams (by pillars or pilasters, if it be a wall), the sound will not travel in this manner; there is always a reflection at each part to the ground below. There is a tunnel connected with one of the railroads in the west of Scotland, in which, as I was informed by Mr. Granger, an engineer, it was utterly impossible for one person to hear another at any distance. It happened, however, that either some pilasters were put along the walls, or the tunnel was made irregular, whereas formerly it had been made smooth, and after that individuals heard

73

each other in any direction, at any distance, with great facility and very distinctly.

You do not suppose this interruption would, in fact, impede the voice from going to the extremity of the room from where the person speaking was?-To a certain extent it would necessarily affect the progress of the sound; but still, if the general outline is alluded to, I believe the diffusion on the whole would be more equal than what it would be without them.

Could it be admitted upon principle, could you beforehand state what amount of ornaments could be safely introduced, or what amount ought not to be introduced, so as to guide the architect in his course?-So much would depend on the particular construction of the building, that I do not see at once that I could answer that, unless the question was subdivided. But this I might say, that I have seen buildings which were entirely covered with ornaments, and that in these buildings the sound of the voice was heard distinctly, and I would only refer to principle, but let applications be made according to the peculiar kind of building to be adopted for the House of Commons; so long as you can bring up a reflecting power to act upon the air, while the direct voice of the speaker is still sounding there, so long you will. strengthen the voice of the speaker; but I found every thing upon this, that the human voice of itself, when it does not meet with interruption, is sufficient to fill the most ample assembly that ever has been made, provided there be no noise from extraneous sources; that you may, if you choose, dispense entirely with the additional power of reflection, and have the walls crowded with ornaments, but taking care there is a perfect power of absorption, so that the audience hear solely by the direct voice of the speaker, and in ninety-nine cases out of one hundred, if the room be moderately quiet, they will hear distinctly; but they will not hear that body of voice which they would have heard had they also gained by the reflection from the roof; and in a building such as the House of Commons, I consider it would not be desirable to take away this reflected strength which may be communicated to the voice; performers on instruments and singers say, when they are in a room which has no reflecting power, that the sound escapes easily enough, but that they do not experience that resilient and sustaining power which makes so many rooms so delightful to speak or sing in; those who pay much attention to the subject feel the tone escaping easily from the mouth, but they do not feel the sound sustained and buoyed up, as it were, where there is too little reflection; in other rooms, where the reverberating power is so great that it

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