WEIGHT OF FUEL. Ill 



"The temperature of the cinders at the time of dumping; 



" The loss of caloric by radiation from the setting of the 

 boiler." 



We must refer to mineral and organic as well as gas 

 analysis to obtain the necessary elements for the distribution 

 of the caloric produced by the combustion of the coal on a 

 steam-boiler grate. 



To avoid referring to them, we will consider the composi- 

 tion and heat of combustion of coal as known. (See tables.) 



WEIGHT OF FUEL. 



The coal used in the test should be kept under cover 

 away from moisture and heat, so- that the hygroscopic water 

 it contains shall vary as little as possible from the time of 

 taking the sample. Weigh the coal in the gross, and then 

 weigh portions of about 100 kilograms (220 Ibs.) on a scale 

 sensible to T ^-^. 



Where practicable, a box open at the top and holding 

 500 pounds of coal should be provided for each 25 square 

 feet grate area, and in proportion for larger grates. It 

 should be placed on the scales, and conveniently located for 

 shoveling into the fire. 



The exact time of weighing should be noted and the 

 exact weight set down. The weight should be taken at the 

 instant of closing the fire-door. The box should be com- 

 pletely emptied each time. The difference of weight at each 

 firing will give the several quantities fired ; the differences of 

 time will give the intervals between firing; and the differ- 

 ence of time between successive charges will serve as a check 

 on the record c ( the test. A chart or diagram should be 

 made showing the regularity of the working, and it is well to 

 keep the records in tabular form ; weights in one column, time 

 in another. 



