EFFECT OF VARIOUS CONDITIONS UPON ECONOMY. 63 



steam is wet and it is used in an engine, the observant engine 

 driver will be aware of the fact by the unusual presence of 

 water in the cylinder. The steam which escapes from the 

 indicator cock, when it is opened, will show an excessive 

 amount of moisture. The water which is discharged by leak- 



t? / 



ing flange joints, or by the leaking stuffing box of a valve in 

 the steam-pipe, will clearly point to wet steam. The moisture 

 will be seen at the vent of the safety valve, if notice is taken 

 of the escaping steam when the valve is opened. These indi- 

 cations can safely be credited when there is more than 3 per 

 cent, of moisture. In regard to the application of this matter 

 to the tests given in the paper, it may be said that there were 

 none of these external evidences of wet steam in any case 

 where the calorimeter trial was not made. 



Little has been said here upon the subject of imperfect com- 

 bustion. It has been incidentally mentioned in the treatment 

 of boiler settings, where the effect of a supply of air above 

 the fuel is considered. That imperfect combustion is a factor 

 in the burning of bituminous coal, the results produced by the 

 admission or exclusion of air clearly prove. That it is also a 

 factor in the burning of other kinds of coal, no one will 

 question. How far it has operated to affect the results of the 

 various tests given, is a matter about which the reader must 

 form his own opinion. The feeling of the writer is that imper- 

 fect combustion, which doubtless existed to a greater or less 

 extent in all cases, is not sufficient to change the general con- 

 clusions thus far set forth. It is highly probable that a full 

 knowledge of the character of the combustion, as determined 

 by analysis of the flue gases in each case, would have furnished 

 a reason for a few individual results, which, in the light of the 

 data at hand, appear somewhat obscure. Doubtless, a knowl- 

 edge of the quality of the various fuels, obtained either by 

 chemical analysis or by determining the total heat of combus- 

 tion, would also have been useful for the same end. The deter- 

 mination of these questions involves labor and expense which 

 few care to undertake, and on this account it is outside the 

 province of tests of limited scope, like those treated of in the 

 paper. 



