be a great expenditure of power in getting that mill into motion, and then a very great wear upon machinery while the mill is in such motion. I am only competent to state the elements of the problem. I have here a little article which I communicated to "The American Architect" on that subject, of which copies can be distributed, and can be included in this publication, as part of the report, if you think it is worth it. I have stated some of the curious facts that have been observed in respect to the vibration of apparently the strongest buildings. One of the most curious cases was that of a stone flax-mill, with arched brick floors, down in New Jersey, of the regular fire-proof English construction, in which a gas-jet was vibrating from the second floor. It was in continual motion with the operation of the machinery. As I have gone about from mill to mill, I have observed that spinning-frames in some mills will ring with a constant "buzz-z-z-z-z." You will feel it really going at a tremendous rate, even on new frames. Go to another part of the mill, and they are still. It has something to do either with the construction or with the mode of building-I don't know which I am not competent to tell. Go into another mill where there are old frames, twenty years old, and in very excellent condition at twenty years old, and you cannot feel the sensation in the frame, although the mill is not what we would build now - it is one that I used to have charge of. There is a cause for this, certainly; and I suspect that the cause is to be found in every building's having its key-note, and that if the revolutions of your machines, or a large portion of those machines, strike that key-note, your whole concern begins to vibrate; it cer tainly seems to be worth a continued series of observations. I think that Mr. Woodbury had better give you some facts that he has observed. These papers, if you care for them, give a computation for the dead weight of machinery in each depart

ment.

Mr. CUMNOCK. Mr. Atkinson has again called our attention to a most important subject, the vibration of mills.

He raises the point that, in some of the mills he has called our attention to, his men found that some of the spinningframes were running still, without any perceptible motion, and no apparent motion in the mill; while one hundred feet or more from this place, in the same mill, the spinning-frames had a perceptible motion, and the mill also. Now, from this

statement the vibration could not be charged to the mill itself, as it gave evidence in some parts at least that it had strength enough, and was well secured to avoid vibration.

If the spinning-frames were running steadily in one part of the mill, and in another part one hundred feet distant there was apparent motion, that fault, in my opinion, was not in the mill, but could be found, I think, in unbalanced cylinders on the spinning-frames.

In passing through a mill not long since, my attention was called to this very fact.

I noticed that there was considerable motion in one part of the mill, and some little distance off there was no apparent motion. I called the attention of the agent to the fact: he said he was aware of it, but had not been able to find the cause. I noticed the motion was uniform. The shafting in the mill was running at a high rate of speed; three hundred and twenty revolutions in the card-room, two hundred and eighty in the weaving, and four hundred in the spinning-room. On the last shaft mentioned, there were two 48-inch pulleys, 24-inch face, running. In standing over them I made up my mind that they were out of balance. I asked the agent to balance them, and see if the uniform wavelet of motion from this point would not He did so, and the vibration of floors and wall ceased. This may seem strange to some of the gentlemen present, but on second thought you will see it is in keeping with laws of motion.

cease.

A regiment of soldiers go over a bridge, and break step, with little or no motion to the structure; cause, broken motion: whereas a dog, on a uniform trot across, will shake the whole

structure.

A pulley unbalanced in the mill, or a spinning-drum running at a high rate of speed unbalanced, will give a uniform motion to every thing in contact with it; and, when fastened to beam or floor, will give the motion to the floors and walls in wavelets. If manufacturers would give more attention to the balancing of pulleys, and machine-makers more attention to balancing the drums, in spinning-frames, the vibration, to a very large extent, in mills would cease.

As to weaving, it is impossible, where two stories of weaving run in the same mill, to run the mill without more or less vibration.

The reason is that all looms have dead points as the crankshaft revolves; there is a throw that cannot be overcome as long as a crank is used for motion. However, the vibration of the mill from the throw of the looms can be reduced very much by breaking the motion. Say 145 picks per minute to be the speed: run every other row of looms three picks above that speed, or below, thus breaking the motion, and the vibration of the mill will be sensibly diminished.

Mr. ATKINSON. I wish to call your attention to the difference between the vibration of the mill, and oscillation of the parts. I think that Mr. Cumnock's explanation will account for oscillation. But there is a law of vibration aside from that, and some of the facts that Mr. Woodbury has observed go far to indicate its nature.

Mr. WOODBURY. Before citing any examples of the jarring of mills, I desire to call your attention to the character of such motions, and to the difference between oscillation and vibration; and then, with this distinction and its causes understood, we will consider a few cases of the vibration of factories, and the nature of the remedy.

The motion of a pulsating body is either oscillation or vibration: the first being caused by external forces; and the second the consequence of forces, one of which is the cohesive force within the body, binding its molecules together, and dependent for its character upon the elasticity of the body. To illustrate: if a suspended wire is struck, the forces of the blow and of gravitation cause it to oscillate; if the same wire is strained. between two points, the forces of the blow and of elasticity cause it to vibrate.

The rapidity of this vibration is governed by the dimensions, elasticity, and tension of the body; and every mass will vibrate at a constant velocity, whenever that vibration is produced by adequate causes and conditions. Not only every piano-forte wire and organ pipe, but every bridge and factory, has its keynote. As the vibrations of the communicating air will force the piano or organ to answer in harmonious response to the tone of the voice, so the structure will reply to the proper vibratory force.

The shaking of a mill is chiefly limited to the vibration of the elastic floor and beams; while the swaying of the whole building is generally caused by oscillation. Both of these

motions appear in the same building; but oscillation is due to poor construction, while vibration is produced by impulses synchronous with the key-note of the building, and bears no relation to the solidity of construction. In a certain district of New England, many factories were built during the war, when high prices, haste for completion, and perhaps limited capital, resulted in poorly constructed buildings. Shabbiness prevails everywhere the walls are too light, the beams too small, and the floor-planks too thin, when compared with structures built by our leading engineers as standards.

In many instances the weight of the machinery has deflected the floors several inches, and in others additional columns have been necessary to keep the floors level. The oscillation of these mills was excessive, but I do not recall an instance of extreme vibration.

In the practical construction of machinery, the revolving portions are not absolutely balanced; and when one considers the immense weight of revolving parts of mill machinery, and its velocity, it seems as if the aggregation of unbalanced centrif ugal forces would overturn, instead of merely jar, a mill; and such a destructive result would undoubtedly ensue if these irregularities acted in unison, instead of opposing each other.

Let us consider the characteristics of a vibrating mill floor by comparison with those of a metal plate when vibrating under conditions which are simple and easily controlled. If a metal plate is supported at the centre, and a violin bow be drawn across the edge, the plate will not vibrate as a whole, but in divisions, which are readily distinguished if sand has been dusted on the plate, as the vibrating portions will jar the sand to the nodes or dividing lines which are at rest. If the plate is a square one, and the bow drawn at the corner while the free vibration is damped by resting the finger at one side midway between the two corners, the sand will gather in two lines, dividing the plate into four equal squares; if the bow is drawn at the middle of one side, and the finger placed at one of the corners, the ridges of sand will divide the plate along the two diagonals extending from corner to corner; and, by varying the positions of the damping points and the bow, the nodal divisions resolve into complex and curious curves and lines. A vibrating mill floor is under similar conditions, except that the contact of pillars and surrounding walls, as far as they

restrain free vibration, complicate the details of these vibrating divisions, beyond the power of analysis, except to show that the vibration of the floor is separated into numerous and irregular divisions.

The effect of these forces has been observed in many factories, and for examples I would refer you to the ring spinningrooms, where the frames are of the same manufacture, and supposed to be operating under identical conditions: some of them will shake violently, while others beside them run as steadily as could be desired.

Some of the gas-pipes extending from the ceiling in the upper story of a flat-roofed mill were observed to be in motion, while others were stationary, showing some of the divisions in the vibrations of the roof. On account of their rigidity, gaspipes do not indicate the divisions of vibration as sensitively as hanging lamps. In a mill at Haydenville, Mass., the vertical motion of certain hanging lamps showed that there was a vibration of the floor amounting to an inch in some places. Other lamps moved less, and some were still.

One of the most delicate indications was in the unoccupied attic of a mill at Exeter, N.H., where the agent had judiciously placed upon the floor numerous fire-pails filled with water. The surfaces moved in unison with the vibration of the floor, generally swaying, some traversed by successive lines of waves whose direction varied in different pails; others, evidently over nodal lines, were at rest; while a few, which were situated upon centres of vibration, were covered with ripples such as are produced when a hanging pail of water is struck underneath. Of two pails situated within a foot of each other, one indicated by its ripples that its position was over a centre of greatest vibration, while the other showed by its wave-like motion that its location was near such a point of greatest vibration, but not over it. The vibrations of the floor are in waves, moving up and down without any progression, and the character of the motions of the water in these pails was concurrent with such action.

It is well known that some notes on a church organ will cause only certain portions of that church to vibrate. I have been informed that in some portions of the picker building of a Woonsocket mill, the vibration jarred the dust to the nodal lines, showing the divisions clearly.