102 BOILEB TE&TS. 



the waste gases shows that the heating surface .by this means 

 was arranged so as to absorb the heat in an efficient manner. 

 The favorable performance of the anthracite coals is borne out 

 by the result of Test No. 28, made with the mixture. It is not 

 so well borne out by the test of the Cumberland coal. Com- 

 paring the different results with that obtained on Test No. 25, 

 made with Lackawanna coal, there is a gain for Lehigh coal of 

 2.8 per cent., a gain for Cumberland coal of 8.2 per cent., 

 and a loss for the mixed fuel of 3 per cent., the comparisons 

 being based on the coal results. These differences seem to 

 be mainly due to the different percentages of ash, for the 

 results based on combustible have an extreme variation of 

 only 2. 5 per cent. In the matter of capacity the Lackawanna 

 coal gave a trifle less than the rated power, the Lehigh gained 

 11 per cent, over the Lackawanna, the Cumberland gained 33 

 per cent, over the same and the mixture 3 per cent. 



The temperature of the escaping gases in the front connec- 

 tion, before passing into the central tubes was 325 degrees 

 higher than that in the flue at the entrance to the chimney. 



Boiler No. 13. 



Kind of boiler, ...... Horizontal return tubular. 



Number used, One. 



Horse-power ( basis 12 sq. ft. ), . . Fifty-five. 



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



Age, Sixteen years. 



Boiler No. 13 is the same boiler as the return tubular boiler 

 given under the head of Boiler No. 1, with the exception that 

 the superheater had been removed. The general form of the 

 boiler and the arrangement of the setting are shown in longi- 

 tudinal section in the following cut. The tests here given ( Nos. 

 29 and 30 ) , were made one year later than Tests Nos. 1 and 2. 



