72 ANNUAL OF SCIENTIFIC DISCOVERY. 



given time, of the necessary quantity. By close observation, by means of 

 an aerometer, the velocity of the entering current was estimated at from 

 8 to 10 feet per second, if the draught was good ; and from 5 to 8 feet 

 when it was but moderate. Again, it was observed that, by admitting 

 the air through numerous thin iilms or divisions, the velocity was neces- 

 sarily reduced, by mere friction, through so many half-inch orifices, as 

 were exhibited in the models and drawings on the table. In the admis- 

 sion of air to the furnace it was shown, that the great object to be effected 

 was, the division of the air on its admission to the furnace so that no 

 more atoms were brought into contact with the atoms of the gas, at any 

 one moment, than were required for their sxiccessive union and combus- 

 tion. If this were the case, combustion and heat would be generated 

 continuously, as the gas and air came into contact. If, however, the air 

 entered in a body, or even in a film, in larger quantities than could be 

 taken up by the gas before the temperature was lowered, a refrigeratory 

 effect must be the consequence, smoke would be formed and fuel would 

 be wasted. It was asserted, that the phrase " burning smoke" was im- 

 proper, inasmuch as the smoke did not exist until the gases had left the 

 furnace. Previously to the introduction of the tubular, in place of the 

 flue system, in marine boilers, it had been supposed, that the introduction 

 of the air, on the Argand principle, by a perforated plate, behind the 

 bridge, satisfied all that nature required in producing perfect combustion. 

 The tubular form of boiler, however, rendered a different arrangement 

 absolutely necessary. This was occasioned by the run, or distance between 

 the bridge and the tubes, being so very short, and consequently, the pass- 

 ing along that distance being so limited in time, that the mixing and com- 

 bustion could not be adequately effected. This, after numerous trials and 

 expedients, led to placing the orifices of admission in the front, or at 

 the door-way end of the furnace. The system adopted by boiler-makers, 

 of contracting the door- ways of marine boilers, much impeded a success- 

 fill application of the Argand principle. The enlarging the door-way 

 opening, however, afforded sufficient space for the required number of 

 three-fourths or one-half inch" orifices. By this arrangement, the length 

 of the furnace, from the door to the bridge, was thus, as it were, added to 

 the length of the run. By this mode of construction, the Argand princi- 

 ple had been applied, with great success to marine boilers. With refer- 

 ence to the supposed necessity for skilful firemen, the paper stated, that 

 the only duty that should be required from the firemen was, the keeping 

 the bars fully and uniformly covered : for if the back end, or the sides of 

 a furnace were left uncovered, the air would pass through them instead of 

 passing through the air- distributors, as that passage offered the hottest and 

 shortest route to the chimney. In fact, it was stated, that unless the bars 

 were well and equally covered, it was impossible to regulate or to control 

 the admission of the air. As to the use of self-acting valves, to regulate 

 the admission of the air, it was stated that after numerous plans had been 

 tried, during the last ten years, all had been discarded in practice, being 



