Directions to be observed in laying the syphon to suit different situations.— First, in laying the pipes of the syphon, it is necessary to give them a regular slope, to admit the air to pass forward into the receiver, or to the highest bends, which must have either an air receiver to each bend, or a pipe inserted to convey the air to a general receiver. Second, when sufficient descent can be obtained on both sides from the air receiver, no air pipes will be required. Third, in situations where it may be necessary to carry the pipes over more than one elevation, and the second exceeds the height of the first, a separate receiver will be required for each elevation. On this construction, viz. with more than one receiver, it is necessary to adopt the following expedient for closing the valves in succession as the air is expelled from each receiver. By. 4 is the lower valve in the receiver s, which is opened by the force produced by pumping, and the air escapes ; t is an inverted valve, with a float v fixed upon the valve spindle in the centre of the cup a. While the air only is expelled, the inverted valve will remain open ; but when the water is forced out and fills the cup, the float will rise and close the valve at the same time; thus the water being stopped from flowing out, will be forced forward to any number of receivers in succession. w is a very small outlet pipe, inserted into the bottom
of the cup is, through which the water escapes slowly; as the cup is emptied the float is lowered, and the inverted valve again opened—a position necessary to allow the air to escape at the next pumping. Another method for closing the valve is shown at Fig. 5. q is a valve placed in a cup, as shown in Fig. 1; on the cup is mounted a lever, with a counterweight x at the one end, and a small pendant receiver y at the other end ; a is a conducting tube inserted into the edge of this cup, to convey the overflowing water into the receiver, which, as it fills, loads the valve and prevents the escape of the water, and thus forces it forward, as before described, to any number of receivers. The preceding account of this valuable improvement in the art of draining, by means of the syphon, is extracted from the original description of it by Mr. Cowen, in the Transactions of the Society of Arts, for the communication of which the Society awarded him the gold Vulcan medal. In the 45th volume of the Transactions are some interesting details of his experiments.