104 BOILEE TESTS. 



The object of the tests on Boiler No. 13 was to determine 

 the effect of two widely different rates of combustion. In Test 

 No. 29, the rate was 12.1 pounds per square foot of grate per 

 hour, and in Test No. 30 it was 6.5 pounds, one giving a slight 

 excess above the nominal power, and the other a much lower 

 capacity. The difference in the economic results of the two 

 tests in favor of the slow rate of combustion is one per cent, 

 based on coal, and 2.3 per cent, based on combustible. There 

 is a noticeable difference in the two tests in the temperature of 

 the waste gases. The excessive temperature with the high 

 rate of combustion, taken in connection with the age of the 

 boiler, gives evidence .of the presence of scale on the heating- 

 surfaces. Had the surface been of sufficient extent, or in such 

 a condition as to absorb this heat, the comparison between the 

 two tests would undoubtedly have been in favor of rapid com- 

 bustion. 



Boiler No. 14. 



Kind of boiler, Horizontal direct tubular. 



Number used, One. 



Horse-power ( basis 12 square feet ), . Fifty-two. 



Kind of coal, ...... Anthracite, Lehigh, Chestnut. 



Age, . . Sixteen years. 



Boiler No. 14 is the same boiler as that referred to as the 

 direct tubular boiler under the head of Boiler No. 1, the tests 

 being made one year later. The general arrangement of the 

 boiler and the manner in which it is set are shown in longitu- 

 dinal section in the following cut. 



In this boiler the products of combustion pass upward from 

 the furnace into a combustion chamber situated in the front 

 end of the shell, then forward through the tubes, then back- 

 ward under the shell to the furnace wall, and finally upward 

 through two side flues and over the top of the rear part of the 

 shell to the chimney flue. The upper part of the shell last 

 traversed furnishes steam-heating surface. This surface is 

 probably inefficient, owing to the deposit of soot which nat- 

 urally covers it. The boiler is fitted with a steam dome. 



