842 TEAXSACTIOyS OF THE AMERICAN INSTITUTE. 



procured at home. We are in search of the truth, and cannot, there- 

 fore cater to national vanity. Our best bituminous and clean, free 

 burning anthracite coals are undoubtedly better than can be found in 

 large quantities in any other part of the globe. All must admit, how- 

 ever, that some of our American bituminous coals are almost identi- 

 cal with the English in appearance and chemical constitution. Both 

 should therefore giv'e the same results, when tested under the same 

 circumstances. In the experiments above mentioned, the English 

 coals comprised a greater number of kinds, the bad being averaged 

 with the good. The United States government experiments M^ere 

 tried with the greatest care, and in a boiler better proportioned for 

 economy, probably, than the average in England. On the whole, we 

 think it fair to assume that the English and American bituminous 

 coals, of the qualities ordinarily supplied to the market, are substan- 

 tially e([ual in value, though selected varieties, fresh from our mines, 

 would of course give much better results. 



The government experiments above mentioned, showed that the 

 evaporative efficiency of the American anthracite, and the American 

 bituminous coals are in the proportion of 8.9 to 0.9. 



The anthracite as a rule, contains much more refuse than the 

 other varieties. The English coals probably average ten per cent 

 of waste the west Pennsylvania and Ohio coals have only five per 

 cent, and the maximum of our bituminous coals rarely exceeds 

 thirteen per cent. On the contrary, the refuse from anthracite rarely 

 falls as low as ten per cent., and often reaches to twenty-four per 

 cent, so that, on the average, its waste is double that of the bitumi- 

 nous varieties. It will therefore be interesting for us to exanrine 

 the results produced by the combustible portions of the different 

 kinds of coal. The part consumed is called the " combustible," and 

 is found by deducting from the weight of the coal the weight of the 

 ashes, clinkers, soot, &c., which can be collected after the trial. 

 Referring again to the navy experiments, we find that the mean 

 evaporative efficiency of thirteen varieties of American antln-acite 

 combustible was equal to the evaporation of 10.69 pounds of water, 

 from a temperature of 212 degrees, and for the three varieties of 

 bituminous combustible, the corresponding effect was 10.84 pounds. 

 The results are practically identical. l)y throwing out of the com- 

 parison some of the varieties of anthracite, which justly have a 

 poor reputation in the market, the preponderance would be upon the 

 other side. If, then, we take it for granted that the average foreign 



