Chapter 2

_Experimental researches_.--All experiments referred to in this paper were made by jets of water under an actual vertical head of 45 ft., but as the supply came through a considerable length of ½ in. bore lead piping, and many bends, a large and constant loss occurred through friction and bends, so that the actual working head was only known by measuring the velocity of discharge. This was easily done by allowing all the water to flow into a tank of known capacity. The stop cock had a clear circular passage through it, and two different jets were used. One oblong measured 0.5 in. by 0.15 in., giving an area of 0.075 square inch. The other jet was circular, and just so much larger than ¼ in. to be 0.05 of a square inch area, and the stream flowed with a velocity of 40 ft. per second, corresponding to a head of 25 ft. Either nozzle could be attached to the same universal joint, and directed at any desired inclination upon the horizontal surface of a special well-adjusted compound weighing machine, or into various bent tubes and other attachments, so that all pressures, whether vertical or horizontal, could be accurately ascertained and reduced to the unit, which was the quarter of an ounce. The vertical component _p_ of any pressure P may be ascertained by the formula--

_p_ = P sin alpha,

where alpha is the angle made by a jet against a surface; and in order to test the accuracy of the simple machinery employed for these researches, the oblong jet which gave 71 unit when impinging vertically upon a circular plate, was directed at 60 deg. and 45 deg. thereon, with results shown in Table I., and these, it will be observed, are sufficiently close to theory to warrant reliance being placed on data obtained from the simple weighing machinery used in the experiment.

_Table I.--Impact on Level Plate._ --------------+--------------------+----------+----------+---------- | Inclination of jet | | | Distance. | to the horizonal. | 90 deg. | 60 deg. | 45 deg. --------------+--------------------+----------+----------+---------- | | Pressure | Pressure | Pressure | | | | / | Experiment \ | / | 61.00 | 49.00 1½ in. < | > | 71.00 < | | \ | Theory / | \ | 61.48 | 50.10 | | | | | | | | / | Experiment \ | / | 55.00 | 45.00 1 in. < | > | 63.00 < | | \ | Theory / | \ | 54.00 | 45.00 | | | | --------------+--------------------+----------+----------+---------- In each case the unit of pressure is ¼ oz.

In the first trial there was a distance of 1½ in. between the jet and point of its contact with the plate, while in the second trial this space was diminished to ½ in. It will be noticed that as this distance increases we have augmented pressures, and these are not due, as might be supposed, to increase of head, which is practically nothing, but they are due to the recoil of a portion of the stream, which occurs increasingly as it becomes more and more broken up. These alterations in pressure can only be eliminated when care is taken to measure that only due to impact, without at the same time adding the effect of an imperfect reaction. Any stream that can run off at all points from a smooth surface gives the minimum of pressure thereon, for then the least resistance is offered to the destruction of the vertical element of its velocity, but this freedom becomes lost when a stream is diverted into a confined channel. As pressure is an indication and measure of lost velocity, we may then reasonably look for greater pressure on the scale when a stream is confined after impact than when it discharges freely in every direction. Experimentally this is shown to be the case, for when the same oblong jet, discharged under the same conditions, impinged vertically upon a smooth plate, and gave a pressure of 71 units, gave 87 units when discharged into a confined right-angled channel. This result emphasizes the necessity for confining streams of water whenever it is desired to receive the greatest pressure by arresting their velocity. Such streams will always endeavor to escape in the directions of least resistance, and, therefore, in a turbine means should be provided to prevent any lateral deviation of the streams while passing through their buckets. So with screw propellers the great mass of surrounding water may be regarded as acting like a channel with elastic sides, which permits the area enlarging as the velocity of a current passing diminishes. The experiments thus far described have been made with jets of an oblong shape, and they give results differing in some degree from those obtained with circular jets. Yet as the general conclusions from both are found the same, it will avoid unnecessary prolixity by using the data from experiments made with a circular jet of 0.05 square inch area, discharging a stream at the rate of 40 ft. per second. This amounts to 52 lb. of water per minute with an available head of 25 ft., or 1,300 foot-pounds per minute. The tubes which received and directed the course of this jet were generally of lead, having a perfectly smooth internal surface, for it was found that with a rougher surface the flow of water is retarded, and changes occur in the data obtained. Any stream having its course changed presses against the body causing such change, this pressure increasing in proportion to the angle through which the change is made, and also according to the radius of a curve around which it flows. This fact has long been known to hydraulic engineers, and formulæ exist by which such pressures can be determined; nevertheless, it will be useful to study these relations from a somewhat different point of view than has been hitherto adopted, more particularly as they bear upon the construction of screw propellers and turbines; and by directing the stream, AB, Fig. 3, vertically into a tube 3/8 in. internal diameter and bent so as to turn the jet horizontally, and placing the whole arrangement upon a compound weighing machine, it is easy to ascertain the downward pressure, AB, due to impact, and the horizontal pressures, CB, due to reaction. In theoretical investigations it may be convenient to assume both these pressures exactly equal, and this has been done in the paper "On Screw Propellers" already referred to; but this brings in an error of no importance so far as general principles are involved, but one which destroys much of the value such researches might, otherwise possess for those who are engaged in the practical construction of screw propellers or turbines. The downward impact pressure, AB, is always somewhat greater than the horizontal reaction, BC, and any proportions between these two can only be accurately ascertained by trials. In these particular experiments the jet of water flowed 40 ft. per second through an orifice of 0.05 square inch area, and in every case its course was bent to a right angle. The pressures for impact and reaction were weighed coincidently, with results given by columns 1 and 2, Table II.

_Table II.--Impact and Reaction in Confined Channels._

+-------+---------+----------+------- Number of column. | 1 | 2 | 3 | 4 -----------------------------+-------+---------+----------+------- Description of experiments. |Impact.|Reaction.|Resultant.| Angles | | | | ABS. -----------------------------+-------+---------+----------+------- Smooth London tube, 1¾ in. | 71 | 62 | 94.25 | 49° mean radius. | | | | | | | | Rough wrought iron tube, | 78 | 52 | 98.75 | 56.5° 1¾ in. | | | | | | | | Smooth leaden tube bent to a | 71 | 40 | 81.5 | 60 sharp right angle. | | | | -----------------------------+-------+---------+----------+------

The third column is obtained by constructing a parallelogram of forces, where impact and reaction form the measures of opposing sides, and it furnishes the resultant due to both forces. The fourth column gives the inclination ABS, at which the line of impact must incline toward a plane surface RS, Fig. 3, so as to produce this maximum resultant perpendicularly upon it; as the resultant given in column 3 indicates the full practical effect of impact and reaction. When a stream has its direction changed to one at right angles to its original course, and as such a changed direction is all that can be hoped for by ordinary screw propellers, the figures in column 3 should bear some relationship to such cases. Therefore, it becomes an inquiry of some interest as to what angle of impact has been found best in those screw propellers which have given the best results in practical work. Taking one of the most improved propellers made by the late Mr. Robert Griffiths, its blades do not conform to the lines of a true screw, but it is an oblique paddle, where the acting portions of its blades were set at 48 deg. to the keel of the ship or 42 deg. to the plane of rotation. Again, taking a screw tug boat on the river Thames, with blades of a totally different form to those used by Mr. Griffiths, we still find them set at the same angle, namely, 48 deg. to the keel or 42 deg. to the plane of rotation. An examination of other screws tends only to confirm these figures, and they justify the conclusion that the inclinations of blades found out by practice ought to be arrived at, or at any rate approached, by any sound and reliable theory; and that blades of whatever form must not transgress far from this inclination if they are to develop any considerable efficiency. Indeed, many favorable results obtained by propellers are not due to their peculiarities, but only to the fact that they have been made with an inclination of blade not far from 42 deg. to the plan of rotation. Referring to column 4, and accepting the case of water flowing through a smooth tube as analogous to that of a current flowing within a large body of water, it appears that the inclination necessary to give the highest resultant pressure is an angle of 49 deg., and this corresponds closely enough with the angle which practical constructors of screw propellers have found to give the best results. Until, therefore, we can deal with currents after they have been discharged from the blades of a propeller, it seems unlikely that anything can be done by alterations in the pitch of a propeller. So far as concerns theory, the older turbines were restricted to such imperfect results of impact and reaction as might be obtained by turning a stream at right angles to its original course; and the more scientific of modern turbine constructors may fairly claim credit for an innovation by which practice gave better results than theory seemed to warrant; and the consideration of this aspect of the question will form the concluding subject of the present paper. Referring again to Fig. 3, when a current passes round such a curve as the quadrant of a circle, its horizontal reaction appears as a pressure along _c_ B, which is the result of the natural integration of all the horizontal components of pressures, all of which act perpendicularly to each element of the concave surface along which the current flows. If, now, we add another quadrant of a circle to the curve, and so turn the stream through two right angles, or 180 deg., as shown by Fig. 4, then such a complete reversal of the original direction represents the carrying of it back again to the highest point; it means the entire destruction of its velocity, and it gives the maximum pressure obtainable from a jet of water impinging upon a surface of any form whatsoever. The reaction noticed in Fig. 3 as acting along _c_ B is now confronted by an impact of the now horizontal stream as it is turned round the second 90 deg. of curvature, and reacts also vertically downward. It would almost seem as if the first reaction from B to F should be exactly neutralized by the second impact from F to D. But such is not the case, as experiment shows an excess of the second impact over the first reaction amounting to six units, and shows also that the behavior of the stream through its second quadrant is precisely similar in kind to the first, only less in degree. Also the impact takes place vertically in one case and horizontally in the other. The total downward pressure given by the stream when turned 180 deg. is found by experiment thus: Total impact and reaction from 180 deg. change in direction of current = 132 units; and by deducting the impact 71 units, as previously measured, the new reaction corresponds with an increase of 61 units above the first impact. It also shows an increase of 37.75 units above the greatest resultant obtained by the same stream turned through 90 deg. only. Therefore, in designing a screw propeller or turbine, it would seem from these experiments desirable to aim at changing the direction of the stream, so far as possible, into one at 180 deg. to its original course, and it is by carrying out this view, so far as the necessities of construction will permit, that the scientifically designed modern turbine has attained to that prominence which it holds at present over all hydraulic motors. Much more might be written to extend and amplify the conclusions that can be drawn from the experiments described in the present paper, and from many others made by the writer, but the exigencies of time and your patience alike preclude further consideration of this interesting and important subject.

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IMPROVED TEXTILE MACHINERY.

In the recent textile exhibition at Islington, one of the most extensive exhibits was that, of Messrs. James Farmer and Sons, of Salford. The exhibit consists of a Universal calender, drying machines, patent creasing, measuring, and marking machines, and apparatus for bleaching, washing, chloring, scouring, soaping, dunging, and dyeing woven fabrics. The purpose of the Universal calender is, says the _Engineer_, to enable limited quantities of goods to be finished in various ways without requiring different machines. The machine consists of suitable framing, to which is attached all the requisite stave rails, batching apparatus, compound levers, top and bottom adjusting screws, and level setting down gear, also Stanley roller with all its adjustments. It is furthermore supplied with chasing arrangement and four bowls; the bottom one is of cast iron, with wrought iron center; the next is of paper or cotton; the third of chilled iron fitted for heating by steam or gas, and the top of paper or cotton. By this machine are given such finishes as are known as "chasing finish" when the thready surface is wanted; "frictioning," or what is termed "glazing finish," "swigging finish," and "embossing finish;" the later is done by substituting a steel or copper engraved roller in place of the friction bowl. This machine is also made to I produce the "Moire luster" finish. The drying machine consists of nineteen cylinders, arranged with stave rails and plaiting down apparatus. These cylinders are driven by bevel wheels, so that each one is independent of its neighbor, and should any accident occur to one or more of the cylinders or wheels, the remaining ones can be run until a favorable opportunity arrives to repair the damage. A small separate double cylinder diagonal engine is fitted to this machine, the speed of which can be adjusted for any texture of cloth, and being of the design it is, will start at once on steam being turned one. The machine cylinders are rolled by a special machine for that purpose, and are perfectly true on the face. Their insides are fitted with patent buckets, which remove all the condensed water. In the machine exhibited, which is designed for the bleaching, washing, chloring, and dyeing, the cloth is supported by hollow metallic cylinders perforated with holes and corrugated to allow the liquor used to pass freely through as much of the cloth as possible; the open ends of the cylinders are so arranged that nearly all of their area is open to the action of the pump. The liquor, which is drawn through the cloth into the inside of the cylinders by the centrifugal pumps, is discharged back into the cistern by a specially constructed discharge pipe, so devised that the liquor, which is sent into it with great force by the pump, is diverted so as to pour straight down in order to prevent any eddies which could cause the cloth to wander from its course. The cloth is supported to and from the cylinders by flat perforated plates in such a manner that the force of the liquor cannot bag or displace the threads of the cloth, and by this means also the liquor has a further tendency to penetrate the fibers of the cloth. Means are provided for readily and expeditiously cleansing the entire machine. The next machine which we have to notice in this exhibit is Farmer's patent marking and measuring machine, the purpose of which is to stamp on the cloths the lengths of the same at regular distances. It is very desirable that drapers should have some simple means of discovering at a glance what amount of material they have in stock without the necessity of unrolling their cloth to measure it, and this machine seems to perfectly meet the demands of the case. The arrangement for effecting the printing and inking is shown in our engraving at A. It is contained within a small disk, which can be moved at will, so that it can be adapted to various widths of cloth or other material. A measuring roller runs beside the printing disk, and on this is stamped the required figures by a simple contrivance at the desired distances, say every five yards. The types are linked together into a roller chain which is carried by the disk, A, and they ink themselves automatically from a flannel pad. The machine works in this way: The end of the piece to be measured is brought down until it touches the surface of the table, the marker is turned to zero, and also the finger of the dial on the end of the measuring roller. The machine is then started, and the lengths are printed at the required distances until it becomes necessary to cut out the first piecing or joint in the fabric. The dial registers the total length of the piece.

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ENDLESS ROPE HAULAGE.

In the North of England Report, the endless rope systems are classified as No. 1 and No 2 systems. No. 1, which has the rope under the tubs, is said to be in operation in the Midland counties. To give motion to the rope a single wheel is used, and friction for driving the rope is supplied either by clip pulleys or by taking the rope over several wheels. The diagram shows an arrangement for a tightening arrangement. One driving wheel is used, says _The Colliery Guardian_, and the rope is kept constantly tight by passing it round a pulley fixed upon a tram to which a heavy weight is attached. Either one or two lines of rails are used. When a single line is adopted the rope works backward and forward, only one part being on the wagon way and the other running by the side of the way. When two lines are used the ropes move always in one direction, the full tubs coming out on one line and the empties going in on the other. The rope passes under the tubs, and the connection is made by means of a clamp or by sockets in the rope, to which the set is attached by a short chain. The rope runs at a moderately high speed.

No. 2 system was peculiar to Wigan. A double line of rails is always used. The rope rests upon the tubs, which are attached to the rope either singly or in sets varying in number from two to twelve. The other engraving shows a mode of connection between the tubs and the rope by a rope loop as shown.

The tubs are placed at a regular distance apart, and the rope works slowly. Motion is given to the rope by large driving pulleys, and friction is obtained by taking the rope several times round the driving pulley.

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A RELIABLE WATER FILTER.

Opinions are so firmly fixed at present that water is capable of carrying the germs of disease that, in cases of epidemics, the recommendation is made to drink natural mineral waters, or to boil ordinary water. This is a wise measure, assuredly; but mineral waters are expensive, and, moreover, many persons cannot get used to them. As for boiled water, that is a beverage which has no longer a normal composition; a portion of its salts has become precipitated, and its dissolved gases have been given off. In spite of the aeration that it is afterward made to undergo, it preserves an insipid taste, and I believe that it is not very digestible. I have thought, then, that it would be important, from a hygienic standpoint, to have a filter that should effectually rid water of all the microbes or germs that it contains, while at the same time preserving the salts or gases that it holds in solution. I have reached such a result, and, although it is always delicate to speak of things that one has himself done, I think the question is too important to allow me to hold back my opinion in regard to the apparatus. It is a question of general hygiene before which my own personality must disappear completely.

In Mr. Pasteur's laboratory, we filter the liquids in which microbes have been cultivated, so as to separate them from the medium in which they exist. For this purpose we employ a small unglazed porcelain tube that we have had especially constructed therefor. The liquid traverses the porous sides of this under the influence of atmospheric pressure, since we cause a vacuum around the tube by means of an air-pump. We collect in this way, after several hours, a few cubic inches of a liquid which is absolutely pure, since animals may be inoculated with it without danger to them, while the smallest quantity of the same liquid, when not filtered, infallibly causes death.

This is the process that I have applied to the filtration of water. I have introduced into it merely such modifications as are necessary to render the apparatus entirely practical. My apparatus consists of an unglazed porcelain tube inverted upon a ring of enameled porcelain, forming a part thereof, and provided with an aperture for the outflow of the liquid. This tube is placed within a metallic one, which is directly attached to a cock that is soldered to the service pipe. A nut at the base that can be maneuvered by hand permits, through the intermedium of a rubber washer resting upon the enameled ring, of the tube being hermetically closed.

Under these circumstances, when the cock is turned on, the water fills the space between the two tubes and slowly filters, under the influence of pressure, through the sides of the porous one, and is freed from all solid matter, including the microbes and germs, that it contains. It flows out thoroughly purified, through the lower aperture, into a vessel placed there to receive it.