40 MR. JOHN GRAHAM ON CONSUMPTION 
Fig. 22. 
I drew the hot air and smoke out of the main flue by 
means of a pump at a temperature of perhaps 6002, forced 
it through the intermediate washing vessel, in which was 
kept a small supply of water, and where mechanical means 
were adopted to subdivide the stream of air, and passed it 
on to the keir. The result of these experiments was a 
failure as regards the heating of the keir. I passed the hot 
air at a high velocity, namely, about 130 cubic feet per 
minute, and found that the heat communicated by the 
mass of air was barely sufficient to sustain the coutents 
of the keir at a temperature not above 190° F., and 
that it took from six to eight hours to bring it up to that 
point. Incidentally, however, I had the means of estimat- 
ing the weight of black smoke. The hot air and smoke 
used were from furnaces that produced dense black smoke 
after each fresh supply of coals. The washing apparatus 
intercepted the soot in such a perfect manner, that the 
water in the keir was not more than discoloured at the 
termination of the experiment. The black residuum in the 
washer, composed of dust and carbon, was carefully ex- 
amined, but not analysed. I formed an opinion to the best 
of my judgment as to the amount of carbon, and as to 
its weight relative to the coal consumed in heating the air 
and smoke drawn by the pump, which was that the weight 
of black smoke does not exceed the one thousandth part 
of the coals consumed. The power of black smoke as 
