APPENDIX. 179 



and expensive, and it is not probable that many engineers 

 will have the instrument as a part of their equipment for test- 

 ing boilers. It is recommended, therefore, that samples of 

 the coal used in testing boilers be sent for determinations of 

 their heating value to a testing laboratory provided with one 

 of these instruments, or with some instrument which shall be 

 proven to be equally good. 



Besides the amendments to the Code of 1885, concerning 

 the determination of "efficiency " and the use of improved 

 steam calorimeters, directions are given for sampling the coal, 

 for determining the heat of combustion from the chemical 

 analysis of coal, and for working out a heat balance. Rules 

 are laid down for finding the quantity of moisture in coal and 

 for making allowance for it. The tabular form of presenting 

 the results of the test is somewhat changed from that of the 

 Code of 1885, and alterations in the text of that Code are 

 made wherever revision seems desirable. 



The Committee approves the conclusions of the Com- 

 mittee of 1885 concerning the standard " unit of evapora- 

 tion " contained in the following extract from the introduction 

 to the Code of 1885 ' 



" It has gradually come to be the custom to reduce all 

 results to the common standard of weight of water evaporated 

 by the unit weight of fuel, the evaporation being considered 

 to have taken place at mean atmospheric pressure, and at the 

 temperature due that pressure, the feed-water being also 

 assumed to have been supplied at that temperature. This is, 

 in technical language, said to be the ' equivalent evaporation 

 from and at the boiling-point ' (212 degrees Fahr.), and has 

 now become so generally incorporated into the science and 

 the practice of steam-engineering that your Committee would 

 simply express their approval of the adoption, and recom- 

 mend the permanent retention of this ' unit of evaporation,' 

 viz., one pound of water at 212 degrees Fahr. evaporated 

 into steam of the same temperature. This is equivalent to 



