BOILERS AND PUMPING ENGINES.

7

attached to it in the usual way; this communicated by a valve with the secondcistern, which latter one was gauged by iveighing water into it as previouslydescribed; it communicated freely with the feed-head, and the supply wasregulated by the float in the boiler in the usual manner ; when the cisternwas emptied, the supply to the boiler was stopped until it was filled again tothe proper level, and the temperatures were taken in the way already described.

In both cases the quantity of water supplied to the boiler every 12 hours wasrecorded. The supply of water to the cylindrical boilers was regulated inthe manner that we always adopt, namely, by constantly admitting such aquantity as shall preserve the level of water as nearly as possible at thesame height; this is done by the stoker working a system of levers com-municating between the stoke-hole, and a cock which is fixed on the pipethat takes the surplus water from the feed-pump; he ascertains the heightof the water in the boilers by means of glass gauges attached to each. Itmay here be remarked that the necessary attention to this keeps the stoker onthe alert, and is, I consider, one of the best safeguards against accident frominefficient supply of water to high pressure boilers.

The coals were actually weighed, not measured, into the stoke-hole, andthe surplus, if any, was also weighed at the end of every 12 hours.

A counter was fixed upon each engine, and the strokes made duringevery 12 hours were recorded.

The Tables referred to in the following remarks accompany this Paper,and at the end of each is an explanation thereof. 4

The coals used during my experiments on both classes of boilers were smallNewcastle coals, of the best quality, supplied by Mr. Charles William Tanner,of the Stratford Coal Wharf, Stratford.

As 80° Fahrenheit was about the mean temperature of the feed-watersupplied to the cylindrical boilers during my experiments, I have adoptedit as the standard temperature; and there is an advantage, I conceive, inthis over a standard of 212°, because the temperature of the feed-water inengines generally is not much above 100°, and seldom below 80°; and, there-fore, for ordinary purposes, the amount of evaporation, without going into cal-culations, will appear rather under-rated than over-rated in my Tables.

Although, for the sake of varying the proportions, I have tried and recorded

4 See Tables I. II. III. IV. V. VI.