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above the surface and vertical. It is found that the water immediately rises in the vertical part, and it must continue to rise until the column produces an outward pressure at the bell mouth equal and opposite to that caused by the motion of the stream. Oscillations are checked by the bulb on the vertical stem and by a diaphram with a small orifice placed across the mouth. If, therefore, h represent, in feet, the height of the vertical column above the surface, we have the velocity of the stream in ft. per sec. expressed by v = 8.024 √h; suppose then it were desired to graduate the tube so that the several numbers on its scale should represent velocity of the stream in miles per hour, we have for one mile per hour (since

22

Fig. 57.

the multiplier or 1.466, alters miles per hour into 15

feet per second)—

(22) 2

I

X × 12 = 0.4 inches;
64.4

:

for one mile per hour, and for other rates, as follows:

Miles per Hour,

1 2 3 4 5 6 7 8 9

Inches from the sur-
face at which the num-
bers 1, 2, 3 are to be 0.4
placed,

1.6 3.6 6.4 1Ο 14.5 19.7 25.8 32.7

It is only necessary that the upper part of the vertical tube be of glass, the lower part may be thin copperplate or other suitable material.

It was by the use of this hydrometer that Pitot overthrew the theory of the old Italian hydraulicians—that the velocity of the several fluid threads in a river increased as the square root of the depth from the surface, and

proved, on the contrary, that the velocity diminished from the surface to the bed, as will be mentioned further

on.

In Figs. 58, 59 are shown Mr. Ramsbottom's excellent apparatus for filling the tenders of locomotive engines with water while running. It consists of an open trough of water, fixed longitudinally between the rails at about the rail level; and a dip-pipe or scoop attached to the bottom of the tender, with its lower end curved forwards and dipping into the water of the trough, so as to scoop up the water and deliver it into the tender tank whilst running along. A part longitudinal section of

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the tender and trough, and part elevation on the right hand, are given in Fig. 58, and a transverse section in Fig. 59.

The water trough A, A, of cast-iron, 18 inches wide at the top, and 6 inches deep, is laid upon the sleepers between the rails, at such a level that, when full of water, the surface is two inches above the level of the rails, its depth being 5 inches. The scoop B (the same letters have the same reference in each Figure), for raising the water from the trough, is of brass, with an orifice 10 inches wide by 2 inches high; when lowered for dipping into the trough, it has its bottom edge just level with

the rails and immersed two inches in the water. The water entering the scoop B is forced up the delivery-pipe C, which discharges it into the tender tank, being turned over at the top so as to prevent the water from splashing over. The scoop is carried on a transverse centre bearing D, and when not in use is tilted up by the balanceweight E, Fig. 59, clear of the ground, as shown by dotted lines, Fig. 58; for dipping into the water trough it is depressed by means of the handle and rod, F, from the foot-plate, which requires to be held by the engine man as long as the scoop has to be kept down. At N is a fixed strong rod supporting the transverse bearing D, D.

DE

AM

6 FEET

SCALE 68

Fig. 59.

The upper end of the scoop B is shaped to the form of a circular arc, as is also the bottom of the fixed delivery-pipe C, so that the scoop forms a continuous prolongation to the pipe when in the position for raising water. The limit to which the scoop is depressed by the handle F is adjusted accurately by set screws, which act as a stop, and prevent the bottom edge of the scoop being depressed below the fixed working level. The orifice of the scoop is formed with its edges bevilled off sharp, to diminish the splashing, and the top edge is carried forward 2 or 3 inches and turned up with the same object.

The principle of action of this apparatus consists in taking advantage of the height to which water rises in a tube, when a given velocity is imparted to it on entering the bottom of the tube-the converse operation being carried out in this case, the water being stationary, and the tube moving through it at the given velocity.

The theoretical height, without allowing for friction, &c., is that from which a heavy body has to fall in order to acquire the same velocity as that with which the water enters the tube. Hence, since a velocity of 32.2 feet per second is acquired by falling freely through 16.1 feet vertical, a velocity of 32.25 feet per second, or 22 miles per hour, would raise the water 16.24 feet: and other velocities being proportional to the square root of the height, a velocity of 30 miles per hour would raise the water 30 feet very nearly (a convenient number for reference), and 15 miles per hour would raise the water 7 feet; half the velocity giving one quarter of the height.

The following Table gives, in the first column, the number of miles per hour at which the train may be advancing; in the second, the equivalent number of feet per second, and the third, the height in feet through which a body must fall, from a state of rest, to acquire that velocity by the action of gravity. The second column is obtained from the first by multiplying the miles per hour by the number 1.466. The third column is the number in the second divided by 8 and the quotient squared :

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In the present apparatus the height that the water is lifted is 7 feet from the level in the trough to the top of the delivery pipe in the tender, which requires a velocity of 15 miles per hour; and this is confirmed by the results of experiments with the apparatus : for at a speed of 15 miles per hour the water is picked up from the trough by the scoop and raised to the top of the delivery pipe, and is maintained at that height whilst running through the trough, without being discharged into the tender.

The maximum quantity of water that the apparatus is capable of lifting is the cubical content of the channel scooped out of the water by the mouth of the scoop in passing through the entire length of the trough: this measures 10 inches wide by 2 inches deep below the surface of the water in the trough, and 441 yards in

20

144

× 441 × 3

)

X

100

16

=

1148 gal

length, amounting to lons, or 5 tons of water. The maximum result in raising water with the apparatus is found to be at a speed of about 35 miles per hour, when the quantity raised amounts to as much as the above theoretical total: so that in order to allow for the percentage of loss that must unavoidably take place, it is requisite to measure the effective area of the scoop at nearly the outside of the metal, which isinch thick and feather-edged outwards, making the orifice slightly bell-mouthed and measuring at the outside 10 inches by 24 inches; this gives 1356 gallons for the extreme theoretical quantity.

The result of a series of experiments at different speeds is that at

15 miles per hour, the total delivery is

=

o gals.

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