To find the total weight or pressure of water to be raised from a well, reckon from the water level in the well to the delivery in the house tank or elsewhere. For example, if the well is 27 ft. deep, and the house tank is 50 ft. above the pump barrel; then you have 77 ft. pressure, or about 39 lb. pressure per sq. in. That portion of the pipe which takes a horizontal position may be neglected. The pressure of water in working a pump is according to the diameter of the pump barrel. Suppose the barrel to be 3 in. diam., it would contain 7 sq. in., and say the total height of water raised to be 77 ft., equal to 39 lb. pressure, multiplied by 7 sq. in., is equal to 539 lb. to be raised or balanced by a pump handle; then if the leverage of the pump handle were, the short arm 6 in. and long arm 36 in., or as 6 to 1, you have (539 × 1) ÷ 56 = 90 lb. power on the handle to work the pump, which would require 2 men to do the work, unless you obtained extra leverage by wheel work. When the suction or delivery pipe is too small, it adds enormously to the power required to work a pump, and the water is then called “wiredrawn.” When pumps are required for tar or liquid manure, the suction and delivery pipe should be the same size as the pump barrel, to prevent choking. The operations of plumbing and making joints in pipes will be found fully described and illustrated in ‘Spons’ Mechanics’ Own Book’; and many other methods of raising water for household and agricultural purposes are explained in ‘Workshop Receipts,’ 4th series. _Purification._--At a recent meeting of the Institution of Civil Engineers, Prof. Frankland read a paper dealing with the question of water purification, in which he remarked that the earliest attempts to purify water dealt simply with the removal of visible suspended particles; but later, chemists have turned their attention to the matters present in solution in water. Since the advance of the germ theory of disease, and the known fact that living organisms were the cause of some, and probably of all, zymotic diseases, the demand for a test which should recognise the absence or presence of micro-organisms in water had become imperative. It was, however, only during the last few years that any such test had been set forth, and this was owing to Dr. Koch, of Berlin. By this means the only great step which had been made since the last Rivers Pollution Commission had been achieved. It had been supposed that most filtering materials offered little or no barrier to micro-organisms; but it was now known that many substances had this power to a greater or less degree. It had also been found that, in order to continue their efficiency, frequent renewal of the filtering material was necessary.