1 82 APPENDIX. 



boiler, its efficiency as a steam-generator, its efficiency and its 

 defects under usual working conditions, the economy of some 

 particular kind of fuel, or the effect of changes of design, 

 proportion, or operation ; and prepare for the trial accord- 

 ingly. 



II. Examine the boiler, both outside and inside; ascertain 

 the dimensions of grates, heating-surfaces, and all important 

 parts; and make a full record, describing the same, and illus- 

 trating special features by sketches. The area of heating 

 surface is to be computed from the outside diameter of all 

 tubes, whether water-tubes or fire-tubes. This rule corre- 

 sponds to the practice of many builders of different types of 

 boilers, and is intended to make the practice of rating heating- 

 surface uniform. All surfaces below the mean water-level 

 which have water on one side and products of combustion on 

 the other are to be considered as water-heating surface, and 

 all surfaces above the mean water-level which have steam on 

 one side and products of combustion on the other are to be 

 considered as superheating surface. 



III. Notice the general condition of the boiler and its 

 equipment, and record such facts in relation thereto as bear 

 upon the objects in view. 



If the object of the trial is to ascertain the maximum 

 economy or capacity of the boiler as a steam-generator, the 

 boiler and all its appurtenances should be put in first-class 

 condition. Clean the heating-surface inside and outside, 

 remove clinkers from the grates and from the sides of the fur- 

 nace. Remove all dust, soot, and ashes from the chambers, 

 smoke-connections, and flues. Close air-leaks in the masonry 

 and poorly fitted cleaning-doors. See that the damper will 

 open wide and close tight. Test for air-leaks by firing a few 

 shovels of smoky fuel and immediately closing the damper, 

 observing the escape of smoke through the crevices. 



IV. Determine the character of the coal to be used. For 

 tests of the efficiency or capacity of the boiler the coal should, 



