METHODS OF CONDUCTING THE TESTS. 13 



be established, on account of the practicable objections and ex- 

 pense involved in carrying on tests of this kind. The 24-hour 

 continuous engineering test is usually out of the question in a 

 mill which uses steam only 10 or 12 hours a day. The six- 

 days' commercial test is not to be thought of by the manager 

 of a mill, who counts the expense for experts' services. The 

 ordinary calls for evaporative tests are for those which can be 

 made in one or two working days, under conditions as near as 

 possible to the existing ones in the locality where the boiler is 

 placed. These must answer, in ordinary practice, for the pur- 

 poses of both the engineering and the commercial tests in the 

 scheme outlined above. 



METHODS OF CONDUCTING THE TESTS. 



Nearly all of the tests referred to in this paper are of the 

 last named class. They were made, as a rule, in factories 

 working 10 or 12 hours per day, where the fires are banked at 

 night, and where an interval of about an hour occurs at noon 

 time, when the production of steam nearly ceases. The boilers 

 were generally cleaned, as far as the outside fire surfaces were 

 concerned, by the use of the tube scraper or steam jet cleaner, 

 preparatory to each test. The inside surfaces were not cleaned 

 and generally were not examined. The mode of firing was not 

 always the best, but it was always good ; that is to say, the fires 

 were, as a rule, free from " holes " or spots where the live coal 

 had died out, with the exception of cases where fine grades of 

 anthracite coal, such as chestnut No. 2 and pea, were used, in 

 which there is frequently a tendency to this state of things, and 

 the fires were kept at a thickness of not less than five or six 

 inches. When bituminous coal was burned, it was usually 

 fired on the "spreading" system, and the bed of coal was 

 broken up and kept level when required by the use of the 

 slicing and stoking bar. 



The method of conducting most of the tests given in the 

 paper is as follows : Preparatory to the beginning of the test, 

 on the night before its commencement, the fires are burned out 

 at the close of the day's work. The furnace and ash-pit doors 



