144 



TRANSACTIONS OF THE 



[FEB. 1, 



other hand, when we regard the capacity to quickly generate 

 great power, run long distances without stopping, and make great 

 mileage before repairs are needed, the locomotive has made great 

 progress. Locomotives which could generate and maintain 500 

 horse power were not common tv^'cnty years since. Now many 

 of the passenger trains require from 80*0 to 1.000 liorse power, 

 and when we recall to mind ihat the measure of a horse ])Ower, as 

 fixed by WuN, is equivalent to raising 33,000 pounds one foot high 

 per minute, we may form some idea of the work accomplished. 

 A few years since, 25,000 to 30,000 miles was considered a good 

 yearly mileage for alocomotive; but now on some roads 10,000 miles 

 per month are often run, and over 100,000 miles per year. In the 

 wood burners of early times, a grate of eight to ten square feet 

 area was sufficient, but when the change was made to coal, and 

 more power required, the grates were enlarged, and in ordinary 

 types of locomotives are now from fourteen to eighteen square 

 feet, and burn from one to two pounds of coal i)er square foot 

 per minute, to do which the blast must be very elficient. 



From a long series of experiments ui)on many railroads, col- 

 lecting and analyzing the escaping gases of combustion, I found 

 that, as a rule, too much air was drawn through the fire-box to 

 produce the most economical combustion of the coal. Some 

 portions of bituminous coal escape partly as black smoke, and a 

 general impression prevails that there is not sufficient air in the 

 fire-box to burn them. This is not the case when the locomo- 

 tive is running. The reason is that the gases have not sufficient 

 temperature for the oxygen of the air to unite with them. For 



First Table. 



Analyses of the Products of Combustion on the P. W. tf- B. R. 

 R., from Engine No. 4:0,vsinf/ Semi-bituminous Coal; Mail 

 Train of 8 Cars. Gas collected between Chester and Wihning- 

 ion, Maij 3, 1878. 



