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eye be directed to two objects at the same time, perception is less in both than if concentrated on one object. Are not cross lights, or rays, approaching the eye in transverse directions prejudicial ? and shall sound, without measure, or adjustment, be communicated to the ear with impunity?
Reasoning further by analogy, the question may be asked, how are such effects produced in Newmachar Church, as are pointed out by those who have preached in it? Does not the soft, absorbent material (as it is termed) diminish sound as much as any thing that we know?_and yet they say that they were heard distinctly at any natural pitch of their voice in all directions, and they believe that similar principles and arrangements may be adopted in apartments of any extent with advantage.
The circumstance alone of speaking without oppression, and with ease in all places where the soft material has been used, is, of itself, very important, as many say they would rather speak a whole day in one place, than two hours in another place. The following hypothesis I believe to be applicable in this case:
If several musical instruments are in tune, and operating in concert, the ear receives their sounds from a distance as of one instrument; but if any instrument gives out discordant sounds, this tends to overcome the more musical sounds, and derange the whole. Precisely such are the effects produced by reflected sounds from the solids in an apartment; in the one case, they give consistent strength and effect to each other, but in the other case they produce discord. If in a room certain of the walls are of solid masonry, and others of lath and plaster, and the ceiling is on the principles of a piano forte sounding board, all having different degrees of action and sound operating in opposition to each other, is it possible that there can be any accordance in the sonorous effects? Causes and effects are in this case similar to that of a complicated piece of mechanism, in which the parts do not fit and move together, but oppose each other; for sound is entirely the offspring of mechanical action in the matter which produces, or conducis, it.
Mode of Regulating Reflected Sounds intended to reach the eur. - The chief objects in the arrangements alluded to, are to obtain reflected sounds of the voice in speech from vertical bodies, so that they may be delivered horizontally on the pinna of the ear, being obviously the direction in which this expanded vibrating lever is best calculated to receive these.
All such reflected sounds must be regulated by the undulatory action in the reflecting solid, each undulation being made to conform in time and duration of sound, as nearly as may be, to the motion of the mechanism of the mouth in the formation of every distinct letter; and these reflections must not be so excessive as to produce any sensible reflection, or echo, from an opposite solid. To effect these objects, soft non-sonorous material is placed behind, and on the edges of the reflecting sonorous bodies, according to circumstances, so as to moderate the reflections, and shorten the undulations.
Nature points out that the reflected sounds of the voice should fall on the ear in a horizontal direction, because the voice proceeds from the mouth in this direction whether we sit, or stand, and, because all cross action in the atmosphere differing from this, is found prejudicial.
Means for Preventing Irregular Sounds from reaching the ear, C.--In order to prevent cross action and derangement in the sonorous atmosphere, and in speech, and to keep extraneous sounds from the ear, a greater proportion of soft non-sonorous material must be placed on the unexposed parts of the ceiling, and on all sonorous bodies that do not reflect horizontally; but this soft non-elastic material must not be exposed to the atmosphere, or the direct action of the voice, except on the floor, because in this case it damps the sound of the voice too much throughout an apartment.* Extraneous sounds may also be operated on by means of rough, or angular, surfaces, so as to cause the particles in the atmosphere to act in opposition to each other, in order to break and divide sound, and thus prevent it froin reaching the ear. Nature exhibits to us the surface of the ground always in a rough state, so as to preveut any moderate degree of sound, such as emanates from the human voice, from occasioning confusion, because the reflections do not reach the ear.
Note.—Lath and plaster are not the most desirable materials for the lining of an apartment; and, in the two Aberdeen charches, the windows are injudiciously and prejudicially placed without sufficient means being adopted to keep back from the ear the intense and irregular sound given ont by the glass.
Glasgow Mech. & Eng. Mag.
FOR THE JOURNAL OF THE FRANKLIX INSTITUTE.
On Breast Water-Wheels. In the year 1833, at page 6, vol. xi, of this Journal, we published an elaborate and able series of experiments, made by Ithamar A. Beard, on the Breast Water-Wheels, driving one of the Hamilton mills, at Lowell, Massachusetts. There were three water-wheels in this mill, each thirteen feet in diameter, and fourteen feet long in the bucket, or having forty-two lineal feet of bucket in all-their tops being level with the surface of water in the head race.
The water was drawn upon each of the water-wheels, during these experiments, by two gates, the upper drawing under a head of about one foot, and the lower drawing under a head of about two feet, so that, although called breast wheels, the water was let on so much above the centre, as probably to render the name of pitch back overshots more properly applicable to them.
The careful experiments above referred to, show that these wheels realized a coefficient of effect of .6019.
Conformably to this result, about sixty per cent. has usually been regarded as the coefficient of effect in breast water-wheels of this
• By the expansion of air in a room, it ascends, and sound with it, acting predominantly on the roof, and little on the floor; soft material may, therefore, be placed on the floor in order to annihilate sound from the feet, &c., without injury to the voice of a speaker.
class, whilst those which draw on their water lower, have been thought even less efficient; but some experiments recently made upon the continent of Europe, develope the singular result, that when nicely constructed, simple breast water-wheels may realize a coefficient of effect of more than eighty per cent!
In other words, that a common breast water-wheel actuated by a fall of water of only about two and three-fourths metres, or nine feet, was, in the case referred to, fully equal in effective power to any over-shot water-wheel!
This being a result equally singular and interesting, we have translated below the experiments which develope it.
Com. Pub. Notes on a Water-Wheel established in a Bleachery at St. Amarin.
By M. MAROZEAU, of Wesserling.- Translated for the Journal of the Franklin Institute, from the “Bulletin de la Société Industrielle de Mulhouse.”
This water-wheel is of the kind called plane bucket, or breast wheel, and is inserted in a circular sweep, or breast. The following figure shows the principal dispositions of a section across the middle of the axis, or shaft, of the wheel:
a b=2.750 metres, or 9.02 English feet; cd=2.674 metres, or 8.77 English feet; e f=0.160 metres, or 0.52 English feet; & h= 0.445 metres, or 1.46 English feet, being the clear depth of the bucket. Diameter of water-wheel about seventeen feet.
The wheel, the breast, and the gates, are of wood, which was adopted for the sake of economy, and executed with all the care and precision desirable. The planes of the buckets are in the direction of the radius.*
The counter buckets (or soleing) leave in the upper part of each bucket a longitudinal opening of .013 metres, or half an inch, in width. Besides the two extreme rings, or shrouding, there are two others intermediate, which divide the buckets into three equal parts. These interior partitions, which add much to the solidity of the wheel, are, moreover, destined to answer another purpose, of which we shall speak further.
The advantageous resulis developed by this wheel with radial buckets, show how unnecessary it is to construct them with elbows, or inclined to the radius; both of which methods, and especially the elbow buckets, are very much used in tbe breast water-wheels of this country.
The circular sweep, in its upper part, is, by a parabolic curve, brought to an even surface, with the portion of a parabola, which forms the sill of the gate; at its lower part it is terminated by a tangent plane, descending about one-tenth of a foot in its length of 9.84 feet, or at the rate of one in one hundred. The outer extremity of this plane, or apron, forms a sill, or step, (.30 met.).98 feet high above the bottom of the tail race. The gate (which is of the waste-board form, so as always to draw on the water from the surface,) has its top formed of a parabola, calculated for a depth of water over it of (.20 met.) or .65 feet. Four partitions, placed opposite to the four rings of the wheel, divide this waste-board gate into three spaces, or bays, the breadths of which are a little less than those of the corresponding portions of the buckets. Each of these bays can be closed by a thick oak plank, so managed by rods that the water may be admitted at will by one-third, two-thirds, or the whole of the gate.
The origin of the fluid vein flowing over the up stream edge of the sill of the gate, is about (.46 met.) 1.50 feet distant from the wheel, so that for a lowering of the gate of (.020 met.) .656 feet, this iluid vein strikes the buckets at a mean vertical depth of (0.40 met.) 1.312 feet, or with a velocity of about (2.80 met.) 9.18 feet per second.
The greater part of these arrangements are comformable to those of wheels before described, and admitted to act satisfactorily; but there are some which appear to me novel, and on them I wish to fix the attention of the “Société Industrielle:" I will speak, first, of the intermediate rings of the wheel, and of the corresponding partitions adapted to the gate; second, of the distance of the gate from the wheel.
We have before stated how we can at will receive the water by the third, the two-thirds, or the whole of the breadth of the gatethe two interior rings dividing the buckets, so that in these several circumstances the water exerts its force on the third, the two-thirds, or the whole of each bucket.
We have adopted this arrangement with the view of making the water act on the wheel in a manner sensibly equal, though very variable, volumes be expended. In effect it is evident that the thickness of the billow of water introduced upon the wheel, has a great influence upon the results, whether by the manner in which it arrives and strikes upon the buckets, or by its mode of action in the circular breast, and in this last respect, notwithstanding the careful construction of the wheel, it is certain, that there is always an appreciable interval between the buckets and the breast, by which a portion of the water escapes without effect on the motor.
The loss of power due to this circumstance being sensibly proportional to the breadth of the breast, we see that so long as this breadth remains the same, the loss affect the result so much the more, as the quantity of water acting may be the less considerable. But if, at the same time that the expenditure of water diminishes, we contract the breadth of the breast, we may hope to establish a sort of compensation leading to very nearly identical results. This, in fact, has now been confirmed by experience.
I come now to speak of the distance of the gate from the wheel, and of the form to be given to that part which forms the waste-board, (or sill over which the water flows upon the wheel.)
M. Morin, in his Memoir on Water-Wheels, (Metz, 1836,) page 66, advises the adoption of waste-board gates placed the nearest possible to the wheel.
Ours is remote, since there exists a distance of (0.46 met.) 1.509 feet between the wheel and the up-stream edge of the sill of the gate.
Thus by this arrangement the fluid vein strikes the buckets nearly perpendicularly, at a point very near the breast, and with a velocity, which, at a mean, only surpasses that of the buckets by about (í metre) 3.281 feet per second, of an opening of 0.20 metre, or .656 feet -a velocity which diminishes in proportion as this opening is itself diminished, but which, nevertheless, always exceeds that of the buckets, a condition indispensable to the proper introduction of the water.
In drawing more of the gate of the wheel, we expose it, on the one hand, to carry the fluid vein upon a part of the bucket very near the soleing, or on this soleing itself; and, on the other, to cause it to strike the buckets at a point where their velocity exceeds that of the entering fluid, which will occasion a shock in a direction contrary to the movement.
Of itself, this observation, which appears not without importance, urges us to declare, that the advice given by M. Morin, in the work before cited, has served, in the main, as the base of the other arrangements which have been adopted for the construction of the wheel; and experiment seems to prove, we have had reason to take it, for á guide.
We will now say a few words on the inclined plane which terminates the circular breast. We find it employed in very ancient water-wheels, and yet in many recent constructions it has been suppressed. This is evidently wrong, for in preserving to the water which issues from the wheel, the velocity which it has in common with the buckets, it is clear we facilitate its disengagement, and we can use this same velocity to repel the water of the tail race, which may thus, without inconvenience, elevate itself to (0.10, or 0.15, met.) .328, or .492, feet above the lowest point of the wheel.
To verify the justness of the principles of which the preceding is an exposition, experiments with the friction brake have been made on the wheel in action.
The brake used is that of the establishment of Bitschwiller, which M. M. Stehelin and Huber have had the kindness to loan us, and which has been applied under the direction of one of their hands accustomed to experiments of this kind. The pulley of this brake is (0.70 met.) 2 296 feet in diameter, on a breadth of (0.26 met.).853 feet; the length of the lever is (3 metres) 9.843 feet..
It was placed on the prolongation of the shaft of the wheel, so that the resistances to be overcome were, besides those of the brake, the friction of the shaft of the wheel on its two bearings, and that of the additional shaft on its single bearing.
We see then that the power consumed by the brake may be sensi