immersed in the water, in which it is kept suspended by a weight x. The pulleys are turned round with great velocity by multiplying wheels, and the cords in their ascent carry up a considerable quantity of water, which they discharge into the box or reservoir z, from whence by pipes it may be conveyed elsewhere. The ropes must not be more than about an inch apart. Emma. What is the reason of that, Papa? Father. Because, in that case, a sort of column of water will ascend between the ropes, to which it adheres by the pressure of the atmosphere. Charles. Ought not this column, in its ascent to fall back by its own gravity. Father. And so it would, did not the great velocity of the ropes occasion a considerable rarefaction of the air near them, consequently the adjacent parts of the atmosphere pressing towards the vacuity, tend to support the water. Emma. Can any considerable quantity of water be raised in this way? Father. At Windsor a pump of this kind will raise, by the efforts of one man, about nine gallons of water in a minute from a well ninety-five feet deep. In the beginning of motion, the column of water adhering to the rope is always less than when it has been worked for some time, and the quantity continues to increase till the surrounding air partake of its motion. There is also another of these pumps at the same place, which raises water from the well in the round tower one hundred and seventy-eight feet in depth. Charles. You told us some time ago, that when we had seen the nature and understood the construction of valves, you would explain the action of the water-press. Father. This is a good time for the purpose, and with it I shall conclude our hydrostatical conversations. You must turn back to the second Plate |