On this principle, a self-acting dam may be raised in any river or stream, up to high-water-mark, by which means a considerable reservoir will be obtained, whilst, during floods, the dam will fold down, and no new ground be overflowed.

In lawns or pleasure grounds, through which streams or rivulets flow, these sluices might be applied to advantage; for, by placing one on the bank of each pond, the water within would always be kept at the same height, whether the weather were wet or dry; and hence flowers or shrubs might be planted close to the water's edge, or in it, (as best suits their respective habits,) and their position with regard to water would always be the same.

Figure 6.

This is merely a different construction of the waster sluice fig. 5.

A, B, is the sluice which turns on pivots at the upper edge A.

C, D, a lever attached to that sluice.

E, a hollow can of cast iron, attached to the extremity of that lever at D, and into which small stones are put until it becomes heavy enough to shut the sluice against the of the water in front. pressure F, a pulley. G, a hollow cylinder of copper (or tin-plate painted,) with a small aperture in its bottom.

D, F, G, a chain, one end of which is fixed to the lever at D, then, passing over the pulley F, has its other end fixed to the cylinder G.

A, H, a tube which communi

cates between the water in front of the sluice A, B, and cylinder G.

When, therefore, the water in front of the sluice is not so high as to flow along the tube A, H, the sluice A, B, remains shut; but when the water rises so as to flow along that tube, it fills the cylinder G which then descending, raises the lever C, D, and can E, and opens the sluice. Again, when the water falls so as not to flow along the tube A, H, the cylinder G is emptied by the small aperture in its bottom, and then the can E shuts the sluice. I erected a sluice of this construction in 1821, at Cartsburn-mill, Greenock. The sluice is four feet long, two and a half feet deep; the lever five feet long from B to D, the cylinder E, sixteen inches diameter, and eighteen inches deep, and filled with small stones till it weighs two hundred and sixty pounds.* The cylinder G, is eighteen inches deep, and the same diameter. This method, wherever it can be adopted, is preferable to that of fig. 5; being simpler and less expensive in the con

struction.

* The quantity of water pressing upon the sluice is twelve and a half cubic feet, or 781 lbs. The pressure at the upper edge of the sluice is to that at its under edge as 8 to 22 nearly; therefore the pivots of the sluice support 208 lbs., which leaves 573 to be supported by the can E; but there is a lever power of two to one, which reduces this weight one half, or to 286 lbs. The weight of the lever C, D, itself, is equal to about 30 lbs. more than the weight of the empty cylinder G; so that the whole weight of the can E, requires only to be 260 lbs.

that few animals, if unprovided with some defence, and if exposed naked

by overflow, it never wastes any water we wish to retain.

A, C, B, L, is part of. a canal, river, stream, or collection of water.

B, C, high-water-mark, or the greatest height to which the water is to be allowed to rise.

B, D, a sluice, or folding dam, which turns on pivots at D.

E, F, a hollow cylinder, having a small aperture in its bottom, to which is joined

E, L, a small pipe always open. I, I, I, I, small holes in the cylinder E, F, on the line of highwater-mark.

G, H, another cylinder, waterproof, that moves up and down freely within the cylinder E, F; and the weight of which keeps the sluice B, D, shut by its connection with

B, K, H, a chain fixed to the cylinder G, H, at H, thence passing over the pulley K, has its other end fixed to the sluice B, D, at B.

When the water in the canal, river, or pond, rises to the line B, C, it passes into the cylinder E, F, at the small holes I, I, I, I; and this lessens the weight of cylinder G, H, so much, that the pressure of the water in front of sluice B, D, throws it open. When the

water subsides, so as not to enter these holes, the cylinder is emptied by the tube E, L, and then the weight of the cylinder G, H, shuts the sluice as before. The dimensions and weight of this cylinder must of course correspond with the weight of the column of water pressing upon the sluice B, D. An apparatus of this kind was first erected at Rothsay in 1817. The dimensions of one of these are:cylinder G, H, two feet diameter, and two feet deep over all; weight 500 lbs.* Cylinder E, F, five feet

This weight is considerably more than necessary when the sluice is placed

ten inches deep, two feet one inch diameter inside: sluice B, D, four feet long and two feet deep.

it

This sluice is here represented with the pivots on which it turns at its under edge, but they may be placed either at the upper or under edge, as circumstances render advisable. The upper edge is also here represented on a level with high-water-mark, but, if necessary, may be placed any where between that and the bottom of the pond or aqueduct, or right below, as on an aqueduct bridge, or similar situation. The cylinders may also be placed on the outside of the dam or embankment, by having a pipe to communicate between them and the water within; but in whatever situation the sluice or cylinders may be placed, the pipe that communicates between the cylinders and the water within the embankment must always have its opening there exactly at the level of high-water-mark, or at the greatest height to which the water therein is to be permitted to rise.

with the pivots at its under, and the chain at its upper, edge; but it was calculated to be powerful enough when the sluice was turned with the pivots at its upper and the chain at its under edge, to which position it has since been changed.

Although the cylinder G, H, requires to be heavier to shut the sluice when its pivots are at the top, yet, to pass the same quantity of water, it does not require to move half so far as when they are at the bottom, and therefore the cylinder E, F, may be made much shorter; so that the cost in either case is nearly the same, or rather in favour of the pivots being at the top. In most cases this last position is preferable; there are instances, however, in which the other is more advisable, such as in a river where wood, ice, or other bulky substances may be expected to float occasionally on the surface; but such cases require a particular construction adapted to the circumstances.

On this principle, a self-acting dam may be raised in any river or stream, up to high-water-mark, by which means a considerable reservoir will be obtained, whilst, during floods, the dam will fold down, and no new ground be overflowed.

In lawns or pleasure grounds, through which streams or rivulets flow, these sluices might be applied to advantage; for, by placing one on the bank of each pond, the water within would always be kept at the same height, whether the weather were wet or dry; and hence flowers or shrubs might be planted close to the water's edge, or in it, (as best suits their respective habits,) and their position with regard to water would always be the same.

cates between the water in front of the sluice A, B, and cylinder G.

When, therefore, the water in front of the sluice is not so high as to flow along the tube A, H, the sluice A, B, remains shut; but when the water rises so as to flow along that tube, it fills the cylinder G which then descending, raises the lever C, D, and can E, and opens the sluice. Again, when the water falls so as not to flow along the tube A, H, the cylinder G is emptied by the small aperture in its bottom, and then the can E shuts the sluice. I erected a sluice of this construction in 1821, at Cartsburn-mill, Greenock. The sluice is four feet long, two and a half feet deep; the lever five feet long from B to D, the cylinder E, sixteen inches diameter, and eighteen inches deep, and filled with small stones till it weighs two hundred and sixty pounds.* The cylinder G, is eighteen inches deep, and the same diameter. This method, wherever it can be adopted, is preferable to that of fig. 5; being simpler and less expensive in the con

struction.

* The quantity of water pressing upon the sluice is twelve and a half cubic feet, or 781 lbs. The pressure at the upper edge of the sluice is to that at its under edge as 8 to 22 nearly; therefore the pivots of the sluice support 208 lbs., which leaves 573 to be supported by the can E; but there is a lever power of two to one, which reduces this weight one half, or to 286 lbs. The weight of the lever C, D, itself, is equal to about 30 lbs. more than the weight of the empty cylinder G; so that the whole weight of the can E, requires only to be 260 lbs.

THE atmosphere is so variable, both

as to temperature and humidity,

that few animals, if unprovided with some defence, and if exposed naked

by overflow, it never wastes any water we wish to retain.

A, C, B, L, is part of a canal, river, stream, or collection of water.

B, C, high-water-mark, or the greatest height to which the water is to be allowed to rise.

B, D, a sluice, or folding dam, which turns on pivots at D.

E, F, a hollow cylinder, having a small aperture in its bottom, to which is joined

E, L, a small pipe always open. I, I, I, I, small holes in the cylinder E, F, on the line of highwater-mark.

G, H, another cylinder, waterproof, that moves up and down freely within the cylinder E, F; and the weight of which keeps the sluice B, D, shut by its connection with

B, K, H, a chain fixed to the cylinder G, H, at H, thence passing over the pulley K, has its other end fixed to the sluice B, D, at B.

When the water in the canal, river, or pond, rises to the line B, C, it passes into the cylinder E, F, at the small holes I, I, I, I; and this lessens the weight of cylinder G, H, so much, that the pressure of the water in front of sluice B,

D, throws it open. When the

water subsides, so as not to enter these holes, the cylinder is emptied by the tube E, L, and then the weight of the cylinder G, H, shuts the sluice as before. The dimensions and weight of this cylinder must of course correspond with the weight of the column of water pressing upon the sluice B, D. An apparatus of this kind was first erected at Rothsay in 1817. The dimensions of one of these are:cylinder G, H, two feet diameter, and two feet deep over all; weight 500 lbs.* Cylinder E, F, five feet

This weight is considerably more than necessary when the sluice is placed

ten inches deep, two feet one inch diameter inside: sluice B, D, four feet long and two feet deep.

it

This sluice is here represented with the pivots on which it turns at its under edge, but they may be placed either at the upper or under edge, as circumstances render advisable. The upper edge is also here represented on a level with high-water-mark, but, if necessary, may be placed any where between that and the bottom of the pond or aqueduct, or right below, as on an aqueduct bridge, or similar situation. The cylinders may also be placed on the outside of the dam or embankment, by having a pipe to communicate between them and the water within; but in whatever situation the sluice or cylinders may be placed, the pipe that communicates between the cylinders and the water within the embankment must always have its opening there exactly at the level of high-water-mark, or at the greatest height to which the water therein is to be permitted to rise.

with the pivots at its under, and the chain at its upper, edge; but it was calculated to be powerful enough when the sluice was turned with the pivots at its upper and the chain at its under edge, to which position it has since been changed.

Although the cylinder G, H, requires to be heavier to shut the sluice when its pivots are at the top, yet, to pass the same quantity of water, it does not require to move half so far as when they are at the bottom, and therefore the cylinder E, F, may be made much shorter; so that the cost in either case is nearly the same, or rather in favour of the pivots being at the top. In most cases this last position is preferable; there are instances, however, in which the other is more advisable, such as in a river where wood, ice, or other bulky substances may be expected to float occasionally on the surface; but such cases require a particular construction adapted to the circumstances.

On this principle, a self-acting dam may be raised in any river or stream, up to high-water-mark, by which means a considerable reservoir will be obtained, whilst, during floods, the dam will fold down, and no new ground be overflowed.

In lawns or pleasure grounds, through which streams or rivulets flow, these sluices might be applied to advantage; for, by placing one on the bank of each pond, the water within would always be kept at the same height, whether the weather were wet or dry; and hence flowers or shrubs might be planted close to the water's edge, or in it, (as best suits their respective habits,) and their position with regard to water would always be the same.

cates between the water in front of the sluice A, B, and cylinder G.

When, therefore, the water in front of the sluice is not so high as to flow along the tube A, H, the sluice A, B, remains shut; but when the water rises so as to flow along that tube, it fills the cylinder G which then descending, raises the lever C, D, and can E, and opens the sluice. Again, when the water falls so as not to flow along the tube A, H, the cylinder G is emptied by the small aperture in its bottom, and then the can E shuts the sluice. I erected a sluice of this construction in 1821, at Cartsburn-mill, Greenock. The sluice is four feet long, two and a half feet deep; the lever five feet long from B to D, the cylinder E, sixteen inches diameter, and eighteen inches deep, and filled with small stones till it weighs two hundred and sixty pounds.* The cylinder G, is eighteen inches deep, and the same diameter. This method, wherever it can be adopted, is preferable to that of fig. 5; being simpler and less expensive in the con

struction.

*The quantity of water pressing upon the sluice is twelve and a half cubic feet, or 781 lbs. The pressure at the upper edge of the sluice is to that at its under edge as 8 to 22 nearly; therefore the pivots of the sluice support 208 lbs., which leaves 573 to be supported. by the can E; but there is a lever power of two to one, which reduces this weight one half, or to 286 lbs. The weight of the lever C, D, itself, is equal to about 30 lbs. more than the weight of the empty cylinder G; so that the whole weight of the can E, requires only to be 260 lbs.

THE atmosphere is so variable, both as to temperature and humidity,

that few animals, if unprovided with some defence, and if exposed naked