io8 Of the Management of Fire 



sive experiment, the real amount of the advantages 

 gained by those flues, or the saving of fuel which they 

 produce. And as I was confident that the suppression 

 of the flue which went round the new boiler would in- 

 crease the draught of the fire-place, and accelerate the 

 combustion of the fuel, I concluded that, if my opinion 

 was well founded with respect to the smallness of the 

 advantages derived from these side flues, the increase of 

 heat arising from the acceleration of the combustion 

 occasioned by the increased draught on closing them 

 up would more than counterbalance the loss of those 

 advantages, and the time employed in heating the water 

 would be found to be actually less than it was before. 



The results of the . following experiments show how 

 far my suspicions were founded : 



Experiment No. 32. The flue round the outside of 

 the new brewhouse boiler having been closed up, and 

 two canals (a and b, Fig. 21) formed from the end of 

 the two outside flues of those situated under the boiler, 

 by which two canals (which were both furnished with 

 dampers) the smoke passed off from under the boiler 

 directly into the chimney, the Experiment No. 31, which 

 was made with the same boiler before the outside flues 

 were closed up, was now repeated with the utmost 

 care, in order to ascertain the effects which the closing 

 up of those flues would produce. The quantity of water 

 in the boiler, and its temperature at the beginning of 

 the experiment, were the same ; the wood used as fuel 

 was taken from the same parcel, and it was put into the 

 fire-place in the same quantities, and at the same inter- 

 vals of time.. In short, every circumstance was the same 

 in the two experiments, excepting only the alterations 

 which had been made in the fire-place. As the length 



