ENGINEERING PROGRESS IN THE U. S. NAVY. 69 



coal, Plate 36 has been prepared. The two fuels were tried under the 

 same boiler, the grates being removed after the coal trials and the fronts 

 rearranged to accommodate the burners and air cones. 



To compare the relative values from this plate, let a ratio of heating 

 surface to grate surface of 40 to i be assumed and a rate combustion of 40 

 pounds of coal per square foot of grate be taken, the coal having a thermal 

 value of 14,500 British thermal units per pound. This rate per square foot 

 of grate gives one pound of coal per square foot of heating surface per hour 

 and a supply to the furnace of 14,500 British thermal units per square foot of 

 heating surface per hour. 



From Plate 36, where this value of British thermal units per hour per 

 unit of heating surface is supplied to the boiler in the form of coal, the conse- 

 quent evaporation from and at 2i2°F. per square foot of heating surface will 

 be 10.8 pounds of water. Should this same amount of British thermal units, 

 14,500, have been introduced into the furnace in the form of oil fuel, the 

 resultant evaporation would have been 11.72 pounds of water. 



One pound of oil, however, may be rated at a thermal value of 19,200 

 British thermal units, therefore the total evaporation per pound of oil would 



be -2 X 11.72 = 15.519 pounds against 10.8 pounds per pound of coal, a 



ratio of 1.437 to i, while, if the thermal values of the fuels be compared, the 

 ratio is 1.324 to i. 



The difference between these ratios, in favor of actual evaporative 

 results, is caused by the elimination of all grate losses and losses due to soot- 

 ing up of heating surfaces when oil is used. 



CONCLUSION. 



With such a large field to cover as suggested by the title of this article, 

 the limitations as to length of the article prohibit anything more than a brief 

 discussion of each point considered, but it is hoped that what has been pre- 

 sented will assure the Society of Naval Architects and Marine Engineers that 

 engineering progress in the naval service has not ceased, and that the Bureau 

 of Steam Engineering, greatly assisted by its co-workers in the development 

 of the Navy, that is, the other technical bureaus of the Navy Department and 

 the engineers of the various shipbuilding yards engaged in naval work, is 

 to-day at least as progressive and as free from ultra conservatism as it has 

 ever been in its history. 



