310 cox. 



The determination of the calorific value of the coal was made in a Berthelot- 

 Mahler bomb calorimeter under a pressure of 20 atmospheres of oxygen. The 

 constants used were those which had been carefully determined for previous work 

 and the corrections for wire fused, niter, sulphur, etc., were made according to the 

 usual methods. 



Color of the smoke. — In judging the color of the smoke the standard Kingel- 

 mann scheme was followed. The smoke was observed against a clear sky and its 

 color compared with the effect upon the eye of a 20-centimeter square, black-and- 

 white grating held at 15 to 20 meters distance. Plate VIII is a photograph of the 

 standard charts used. No. 1 is the pure white paper, and No. 6 in the series 

 is entirely black ; hence each intermediate proportion corresponds to a 20 per 

 cent range. Plate IX shows a small section of the upper left-hand corner of 

 each grating drawn to the exact scale. 



Method of firing. — It was found that all of these coals, except where 

 there was a large amount of clinker, worked best when fired in small 

 quantities every four or iive minutes with spreading stoking. 



Method of starting and stopping. — The alternate method was used, 

 that is, the boiler was thoroughly heated by a preliminary run of an 

 hour or more; during the last twenty minutes or half an hour of this 

 time the fire was fed with the coal to be tested, then allowed to burn 

 low, cleaned, left level and the amount of live coal left on the grate 

 estimated. At the same time the pressure of steam, the water in the 

 boiler and other observations were taken, and the time recorded as the 

 starting time. Fresh coal which had been previously weighed was now 

 fired and the ash pit cleaned immediately. Before the end of the trial 

 the fire was allowed to burn low, just as before the start, again cleaned 

 and left in the same condition and with the same amount of coal on the 

 grate as at the beginning of the test. This stage was recorded as the 

 stopping time. 



The temperature of the fire room was not recorded, because in the 

 tropics fire rooms are so constructed that when in use they are entirely 

 open and are practically the same as if the stationary boiler had merely a 

 roof over it. The fire room temperature may be taken as that of the air. 



The ash represents that actually removed. It was not practicable to 

 recover the ash carried over the bridge and into the flues. 



The individual tests give the other conditions governing the trials. 

 I have been guided in reporting the data and the results of these evapora- 

 tion tests by the form advised by the Boiler Test Committee of the 

 American Society of Mechanical Engineers,^^ and have made these as 

 complete as possible to enable an3'one to make whatever other calculations, 

 he may desire. 



TESTS. 



The following tables give the complete data obtained during and cal- 

 culated from the various tests on coals made in this Bureau : 



"Code of 1899, Kent's Mechanical Engineers' Pocket-Book, New York (1903), 

 690; Univ. of III. Bull. (1906), 3, 21; International Library of Technology 7, 

 36; etc. 



