THE simple method of measuring the discharge of water-pipes considered here is not new, but it does not seem to have received the attention it deserves. Stated briefly, a small quantity of colour is put into the pipe at one point, and the time taken till it appears at another point at a known distance along the pipe, and hence the velocity is calculated. Simple enough, no doubt; but does it give accurately the mean velocity of the water in the pipe? The point that seems to have escaped notice is that this method does give the mean velocity, and gives it to a degree of accuracy quite sufficient for most engineering requirements. And the cost of a test is practically nothing, as no elaborate fittings in the way of weirs or gauges are required. This method was used by several members of the School of Mines staff to test the flow of a concrete water-main laid by the Ballarat Water Supply Commission. Incidentally, it may 'be noted that a weir at the intake end would have seriously interfered with the levels in the supply channel, and at the discharge end would have been impossible under normal conditions, as the channel would be in use drawing water from one of the reservoirs. A method was required that could be used periodically to test the condition of the pipe. The pipe is 4 3/4 miles long, 24-in. internal diameter, made of reinforced concrete, and laid on a uniform grade of 0.63 in. per chain. It joins an inverted syphon of 14-in. C.I. pipe,_x000D_
mile long, and discharges into an open channel. At intervals along the pipe there are vertical air-vents, which made the use of the colour and accurate measurement of the water-level an easy matter.