METHODS OF CONDUCTING THE TESTS. 19 



The superheating calorimeter, which is shown in the ap- 

 pended cut, works on a different principle, requiring no water 

 and no weighing. It consists of a heater, through which the 

 steam to be tested is passed, and in which the moisture con- 

 tained is evaporated. This apparatus determines the quantity 

 of moisture, by first measuring the quantity of heat expended 

 in evaporating it, and this is readily done by supplying the 

 heater with steam previously superheated and observing the 

 fall of temperature which the steam suffers in passing through 

 the heater. The principal data required are the temperatures 

 given by three thermometers, which do not need to be of deli- 

 cate construction, nor to be read with extreme care. The quan- 

 tity of moisture is readily determined to a small fraction of one 

 per cent., since a fall of some 18 degrees in the temperature 

 of the supply of steam to the heater is required for one per 

 cent, of moisture. 



The steam which is supplied to the calorimeter, whichever 

 form is employed, is taken from the main discharge pipe of the 

 boiler by means of a well covered half-inch pipe. A long 

 thread is cut upon the pipe, and it is screwed . into the 

 main so as to extend across the whole diameter of the pipe, 

 and the enclosed portion is perforated. In this manner the 

 points of supply are distributed and a sample of the steam is 

 obtained. 



EXPLANATION OF THE TABLES OF PART SECOND. 



Referring now to the various tables of results given, some 

 explanation is needed as to the meaning of the lines and the 

 method of computation employed. 



When the " manner of start and stop and kind of run " is 

 stated to be ordinary , reference is made to the method just de- 

 scribed, the tests beginning early in the morning, after the 

 boiler had stood with no fire and with closed dampers during 

 the preceding night, and with no preliminary heating ; there 

 being an interval at noon-time when the production of steam 

 nearly ceased, and the night evaporation being included in the 

 total. When " manner of start and stop and kind of run " is 



