HOW THE THE TESTS WERE CONDUCTED. 13 



MEASUREMENT OF THE FEED-WATER. 



How the feed-water should be measured is a matter which 

 depends somewhat upon the arrangement of the plant and the 

 type of apparatus used for feeding the boilers, and this must in 

 a great many cases be adapted to the local conditions. It is 

 always best to weigh the water, and for this purpose to erect 

 tanks and scales suitable for the work. There are instances, 

 however, where it is impossible to do this, because it is neces- 

 sary that water should be available under some head so as to fill 

 the weighing-tank, which is generally elevated several feet 

 above the pump ; and there are cases where no water is at hand 

 under the necessary head. A meter .can be employed in such 

 cases, or the water may be supplied through an orifice of known 

 size arranged so as to be calibrated. In most cases, however, 

 the system of measurement by weighing can be employed ; and 

 wherever it can be done, the method is to be followed in prefer- 

 ence to all others. The simplest apparatus of this kind, having 

 a capacity of say 6,000 Ibs. of water per hour, consists of a 

 small hogshead connected to the suction-pipe of the pump or 

 injector, and an ordinary oil-barrel mounted on platform scales, 

 the latter being supported by the hogshead on one side and by 

 a suitable staging on the other side. The barrel is filled by 

 means of a cold-water pipe leading from the source of supply, 

 and this should be 1" pipe for pressures not less than 25 Ibs. 

 The outlet valve of the barrel is attached to the side close to 

 the bottom, and this should be at least 2" in diameter for quick 

 emptying. Where larger quantities of water are required, the 

 barrel can be replaced by a hogshead, and two additional hogs- 

 heads can be coupled together for the lower reservoir. The 

 capacity reached by this arrangement when the weighing hogs- 

 head is supplied through a 2" valve under 25 Ibs. pressure, 

 and emptied through a 5" valve, is 15,000 Ibs. of water per 

 hour. For still larger capacity it is desirable to use rectangular 

 tanks made for the purpose, and have the weighing-tank arranged 

 so that the ends overhang the scales and the reservoir below, 

 the outlet valve, consisting of a flap valve, covering an opening 



