METHODS OF CONDUCTING THE TESTS. 17 



plies eight times, which is a sufficient increase, gives a move- 

 ment of 4 inches for an actual draught of half an inch ; that is, 

 for a draught corresponding to the pressure of a column of 

 water half an inch high. 



The quality of the steam, in the case of boilers giving super- 

 heated steam, is determined by taking its temperature. A 

 thermometer is inserted for this purpose in an oil cup, which is 

 screwed into the main discharge pipe. The quantity of super- 

 heat is the number of degrees which the indicated temperature 

 is in excess of the normal temperature. The normal tempera- 

 ture is that indicated by the thermometer when the boiler is 

 under steam of the average pressure, at a time when the pro- 

 duction has ceased, that is, when the steam is in a saturated 

 condition . 



In the case of boilers which do not superheat the steam, the 

 quality is determined by the use of a calorimeter. The form 

 of calorimeter employed is sometimes the barrel calorimeter, 

 but preferably the continuous superheating calorimeter, devised 

 by the author. The barrel calorimeter consists of a common 

 oil barrel, fitted Avith an outlet valve, together with delicate 

 scales and a finely graduated thermometer. A series of tests 

 is made, one following after the other as rapidly as possible 

 and the results are averaged. The barrel is first filled with 

 water to the desired point and the water heated in preparation 

 for the tests. This water is let out and thrown away. The 

 barrel is then filled again and the average temperature of the 

 incoming water is taken, read to tenths of a degree, and the 

 weight of water drawn in is carefully determined. After blow- 

 ing out the condensed water from the pipe which is provided 

 for supplying the calorimeter, a movable piece of pipe which 

 conducts the steam into the water is attached, and the valve is 

 opened for the formal conduct of the test. The water is 

 heated to about 110 degrees. Then the valve is shut, the 

 movable pipe unscrewed, the water stirred and the temperature 

 carefully observed. The weight is taken, and the quantity of 

 steam condensed is found by subtracting the previous weight. 

 Each test of the series is conducted in the same manner, except 



