NO. 3 LANGLEV MEMOIR ON MECHANICAL PLIGHT 75 



" 2. What is the relative efficiency of the initial and final halves of the 

 length of the boiler? This will show in how far it is useful to increase the 

 length of the boiler for a given burner and steam jet. It will also show what 

 advantage is to be gained from triplicate boilers with three burners, as compared 

 with duplicate boilers with two burners, or single boilers with one burner, when 

 the same weight of tubing is used throughout. 



" 3. What is the effect of pressure on the aeolipile tank, or in how far does 

 the steam generated depend on what may be called the pressure of the flame ? 

 This is also an important point which remains for quantitative solution. It can 

 be approached in two ways : either by finding the steam evaporated in terms of 

 the tank pressure, or by finding the temperature of the flame pyrometrically. 



" 4. What speed of water circulation best conduces to steam generation? 

 A good pump is now installed by which the circulation can be varied. If water 

 can be put into the boiler just fast enough to come out dry steam at the other 

 end, the efficiency ought to be a maximum, but it docs not follow that it will be 

 so, for one can imagine a wet circulation sponging up more heat than one which 

 is just dry at the end." 



1895 



During January and February, 1895, the experiments with boilers and burn- 

 ers were continued and even better and more uniform results than those given 

 above were obtained. The boilers of Aerodrome No. 5 were finally brought to 

 such a state of efficiency, that under favorable conditions a lift of nearly sixty 

 per cent of the flying weight was secured. This was much more than was re- 

 quired for flight, but it was decided to postpone the trials until No. 4 could also 

 be made ready for a test and the frame of No. 5 could itself be strengthened in 

 many weak places. 



Upon examining No. 4, which had been put aside since the trials in De- 

 cember, it was found to have rusted so badly throughout and to be so unfit in 

 every way for trial, that a complete reconstruction of the whole would be neces- 

 sary. So many advantages had been gained in No. 5 by the double midrod type 

 of construction that it was decided to rebuild No. 4 on a modification of the same 

 plan, as shown in Plate 11, retaining, however, the same engines which had been 

 used before. 



In this a very guarded return was made to the type which had proved so 

 unsatisfactory in No. 0, that is, making the hull support rods at the front and 

 rear for attaching the wings and tail. In this case, however, the hull was con- 

 structed very rigidly, and the tubes at the front and rear were firmly attached 

 and braced so that they could withstand a considerable strain without undue 

 distortion. The work on this frame was completed in March, but the other parts 

 were not in entirely efficient condition even in May, when the aerodromes were 

 taken to Quantico for trial. Moreover, it was found that the weight of this 

 aerodrome had increased far beyond the original estimates. 



