Water force. Without entering here into details on moving forces which have been forwarded either to Mechanics or Geometry, we will contain ourselves only to the force of water.

Force, its expenditure and the speed of water are often confused by other authors; that is the effort that water makes to exit and expel itself against a column of air which resists and weighs onto it. It depends therefore on two points, the column of water and the column of air. See Column.

The speeds are as the square of the distance of the heights or by reason of the involutes of their heights If the height of one reservoir is 16 feet and the other 25, the speeds (presumably as the water is expelled) are as 4 is to 5, since 4 is the root of 16 and 5 is the root of 25.

One can evaluate the force of a man who uses a motor pump manually by adding approximately 25 pounds when he makes this pump work effortlessly; that a horse which makes a millstone turn is the example that we have taken and it is estimated to be equivalent force of seven men: in such a way the force is equal to seven times 25 pounds which is 175 pounds. See the following article. We know that 10 pounds of force support in equilibrium 10 pounds of water and that it requires 10 additional pounds of force to force it to increase. Based on this principle, a man who is the motor force of a manually operated pump if he uses the handle and if he uses 11 pounds of force he will move 10 pounds of water into the air, supposing that there is no friction and to which we would add one third additionally into the calculations.

If for example the weight of the body that we wished to elevate is 90 pounds, one must add that to the sum 1/3, which is 30, to elevate it and to overcome the resistance from friction which altogether is 120 pounds of force and will then elevate a column of water of 90 pounds in weight. One evaluates the force or the speed of a current, of a river, of the stream, of an aqueduct by determining the base of one's discretion as well as the way in which a ball of wax placed on the water and a stopwatch, then one will know the amount of time the ball has been carried by the current, and we are able to determine the distance from the base is approximately 20 toises. If the ball has travelled for 30 seconds, one half of a minute, in its course, it would have been 20 toises or 120 feet in 30 seconds or 4 feet per second; then one would multiply this speed by 4 feet which is the width of the stream that is estimated here to be 12 feet, and which would provide 48 ft.² per second as the area of the canal. Take the depth of this canal or stream, for example 2 feet, which by multiplying the 48 feet of the area, will give you 96 feet for the depth of water flow which will exit or spill out in the space in one second: it is 96 ft.³ multiplied by 35 which is the value of the cubic foot or 3360 pints of water which will spill out per second. There is another method in which a ball of wax can be used to determine the speed of a river; it is located in the memoir is of the Academy of sciences years 1733, page 363. See also the word River.