NO. 3 LANGLE* MBMOIB OS MECHANICAL PLIGHT 35 



tlieni in this respect, regardless of the absolute economy of fuel that might or 

 might not be exhibited. Hence, to the end of my experiments nothing else was 

 used. 



P]ven before the "beehive" boiler was completed, I was anxious to ascertain 

 what could he done with a coil of pipe with a stream of water circulating through 

 it, as well as with various forms of burners, for I realized that the success of the 

 apparatus depended not only upon getting an exceedingly effective heating sur- 

 face, hut also an equally effective flame to do the heating. 



For fuel I naturally turned to the liquids as being more compact and readily 

 regulated. "Whether to use some of the more volatile hydrocarbons or alcohol, 

 was slid an unsolved problem, but my opinion at the time was that, on the lim 

 ited scale of the model, better results could probably be obtained with alcohol. 



In the experiments made with a coil preliminary to the trial of the " bee- 

 hive " boiler, I tried a simple horizontal coil of |-inch copper pipe into which 

 two forked burners working on the Bunsen principle and using city illuminating 

 gas, were thrust. The jets were about \ inch apart. The arrangement primed 

 so badly that the engines could not get rid of the entrained water, and would only 

 make a few turns. 



I then tried the same coil with two 1.25-inch drums in the inside and with 

 five longitudinal water tubes at the bottom, beneath which were the same two 

 forked burners used in the previous experiment. The coils were covered with 

 a sheet of asbestos, and two round burners were added. This boiler would hold 

 a steam pressure of about 15 pounds and run the engine slowly; but if the pres- 

 sure were allowed to rise to 60 pounds, the engine would drive a 2-foot propel- 

 ler of 18-inch pitch at the rate of about 650 turns per minute for from 80 to 90 

 seconds, while the steam ran down to 10 pounds, showing that this boiler, at 

 least, was too small. This was further shown in a trial of the plain coil made 

 in October, 1891 ; 6 pounds of water were evaporated in 32 minutes under a pres- 

 sure of 60 pounds. This was at the rate of 11.25 pounds per hour, or, taking 

 the U. S. Centennial standard of 30 pounds of evaporation per horse-power, 

 gave an available output of less than \ horse-power. 



With these results before me, I decided to make a trial of the " beehive ' 

 principle upon a smaller scale than in the boiler designed for Aerodrome No. 0. 

 I used a small boiler of which the inner coil consisted of 8 turns of g-inch cop- 

 per tube about 28 gauge thick, and the outer coil of 11 turns of }-inch copper pipe. 

 This gave 12 feet of 3-inch, and 16 feet of {-inch tubing. The drum was of No. 

 27 gauge, hard planished copper. "With this boiler consuming 6 oz. of fuel, 80.3 

 oz. of water were evaporated in 28 minutes, or at the rate of about 10.75 pounds 

 per hour. As these coils contained but 2.22 square feet of heating surface, and 

 as the three to be built would contain 3.7 square feet each, it was estimated the 



