Memorandum on the Newcastle Ejigine Trials. 073 
found that the boiler could not be worked at a lower pressure 
than 35 lbs. to the square inch, because water was so abundantly 
ejected with the steam. At 98 lbs. pressure, 5'85 lbs. of water 
were evaporated from 49° by 1 lb. of inferior coal, while at 
35| lbs. pressure, 6-48 lbs. were evaporated from 47|^°, or nearly 
the same temperature. The units of heat imparted per 1 lb. of 
steam were only as 1167"5 is to 1152-3, and the evaporation at 
the lower pressure should only have been 5*94 lbs. of water per 
1 lb. of coal, instead of the quantity given above. The excess, 
amounting to 9 %, was due probably to the increased difference 
of 55° between the temperature of the water in the boiler and 
the furnace, and no doubt also, to some extent, to priming. 
The method of ascertaining the rate of cooling was not 
satisfactory. It was impossible to seal the ash-pans and 
the fire-box and smoke-box doors completely, so as to prevent 
all access of cold air to the inside of the boiler ; and the condi- 
tions during cooling were not the same as when the engines 
were at work, for the observations commenced generally in the 
evening when the weather was colder, and the runs took place 
in a covered shed, while the cooling proceeded in the open air. 
In future efficient means of closing the chimney should be 
provided, and the sheds should be made roomy enough to allow 
the engines to coal in the same place where they worked. 
With respect to the general conduct of the trials, it would 
be well that on a future occasion there should be two weighing 
machines appropriated to each engine. One should be fitted 
with a coal-box large enough to hold the whole of the coal 
required for the trial run, and should be so arranged that the 
driver could fire direct from it ; and the second machine should 
be fitted with a water tank capacious enough to hold the whole 
quantity of water likely to be used. The weight of coal and 
water should be taken every ten or fifteen minutes, so that the 
rate of consumption throughout the run might be ascertained, 
and all chance of error avoided. It may, indeed, be necessary 
in some cases — when, for example, the condensed steam from the 
feed heaters is returned to the feed tanks — to use two small 
supplementary tanks and weighing machines besides the main 
feed tank, in order to gauge correctly the quantity of water 
evaporated. 
It is desirable to alter the revolution counters on the brakes, 
so that the figures should appear clearly on the revolving dials, 
in order that the number of revolutions may be easily read off 
while the counters are running ; and this reading should be taken 
simultaneously with the observation on the weight of coal and 
water. By taking these precautions, a run will not be lost in 
VOL, XXIV. — S. S. XX 
