54 ANNUAL OF SCIENTIFIC DISCOVERT. 



formed should be blown off every evening when the water has cooled down; 

 in marine boilers, the carbonate will float near the surface when the boiler is 

 working, and it can be blown off by the surface water-cock. Any alkali will 

 neutralize the sulphate of lime in a steam boiler, but the common carbonate 

 of soda is the cheapest which can be used. Care, however, must be exercised 

 not to employ it or any other alkali in excess for such a purpose, as it has a 

 tendency to volatilize with the steam. 



CONSUMPTION OF COALS AND RATE OF EVAPORATION FROM ENGINE 



BOILERS. 



At a recent meeting of the Manchester Philosophical Society, Mr. Graham 

 read a paper, in which he described the results of experiments which he had 

 made with a series of small vessels of equal size, the fire being under the 

 first, and the flame-bed alone passing under the others. The evaporative 

 power of the first was found equal to 100, the second to 27, the third to 13, 

 and the fourth to 8. A second set of experiments with larger vessels, in the 

 shape of boilers, corroborates these results. The third scries of experiments 

 were made with the view of determining the value of a supplementary boiler 

 as a heating surface, placed under the most favorable circumstances ; the 

 result showed an advantage of 15 per cent. 



Mr. Graham then detailed the results of a numerous set of experiments on 

 evaporation, on the large scale, with reference to engine boilers. These ex- 

 periments have extended over a period of several years, observations being 

 made daily, and the results deduced from several hundred recorded observa- 

 tions. Before beginning to register his results, the boilers were in each case 

 reset, and by careful and continuous experiments were put into what was 

 found to be then their best condition for giving the best working result, as 

 regards the admission of air, the draft of the chimney, the size of the fire- 

 place, the distance of the bars from the boiler, the thickness of the fire-bars, 

 and of the fire itself, the form of the flame-bed, flues, and bridges. Mr. Gra- 

 ham stated that in the case of one boiler, the alterations had been repeated 

 at least 30 times for this purpose. The experiments with the boilers were. of 

 12 hours duration each, and number from 30 to 40 for each boiler. A perfect 

 command was maintained of the draft, which varied from 0'5 to 0'7 in. pres- 

 sure of water, and the temperature of the draft at the bottom of the chim- 

 ney was generally sufficient to melt lead (612 J F.), but never zinc (773 F.) 

 The conclusions which Mr. Graham arrived at by means of these experiments 

 were the following: 



1. That the boiler usually called the " Butterfly, or Fishmouth boiler," 25 

 feet long and 7 feet diameter, will, under favorable, but what may be called 

 ordinary circumstances, give with the Worsley coal, for each pound of coal 

 burnt, 8'29 Ibs. of steam; or, not including the heating of the feed- water, from 

 60 to 212 F., 9'67 Ibs. 



2. The boiler usually known as James Watt's " wagon-shaped boiler," 25 

 ft. 6 ins. long, and G ft. G ins. diameter, will, under similar circumstances, 

 give 8'SO Ibs. of steam; or, not including the heating of the feed-water, from 

 60 F. to 212 F., 10*26 Ibs. of steam for each pound of coal burnt. 



3. The plain cylindrical boiler, with fire-place underneath, 42 feet long and 

 G feet diameter, will, under similar circumstances, give G'20 Ibs. of steam ; or, 

 not including the heating of the feed-water, from GO F. to 212 F., 7'23 Ibs. 

 of steam for each pound of coal burnt. 



