Nil. 3 LANGLE1 MEM0IB ON MECHANICAL FLIGHT 59 



almosl as well as one, the reason apparently being that the rapid circulation in- 

 creased the steam generating power of the boiler, and that the engines worked 

 best at about 80 pounds. II was also found that a larger tubing was better than 

 the small, weight for weight, Ibis fad being due to the greater ease wilb which 

 circulation could be maintained, since fewer coils were necessary in order to 

 obtain the same external heating surface. The pressure in the coils and tbe 

 separator was also much more nearly equalized. Tbe result was that tbe boiler 

 temporarily approved was one made of tubing- 6.35 mm. (0.25 inch) in diameter, 

 bent into a two-eoil, two-stranded boiler, having sixteen complete turns for each 

 strand in each coil. Tbe total weight was 5G0 grammes (1.23 pounds) with a 

 total heating surface of 1300 sq. cm. (1.4 sq. ft.). 



The separator used in tbe experiments made during August and September 

 was of a form in which the water was forced below a series of partitions that 

 prevented it from following the steam over into the cylinders of the engines. It 

 weighed 410 grammes (0.9 pound) and was mosl conveniently worked with 700 

 grammes (1.54 pounds) of water. Tbe boiler and separator together weighed 

 970 grammes (2.1 pounds). 



A new separator was, however, designed, which was horizontal instead of 

 vertical, as it was intended that it should be placed just below the midrod. An- 

 other form, devised for constructional reasons, consisted of a cylinder in which 

 a puuip was imbedded. Heretofore the pump used had been single-acting, but it 

 was now proposed to make ;i double-acting pump. Upon testing this apparatus, 

 it was found that when using an aeolipile, it took 150 grammes of alcohol to 

 evaporate 600 grammes of water. It was evident that the latter was used very 

 wastefully, so that the thermal efficiency of the engine was not over one per cent; 

 but it was also evident that, under the necessity of sacrificing everything to light- 

 ness, this waste was largely inevitable. 



About tbe middle of October, another boiler (O, Plate 13) was made, which 

 consisted of two coils wound in right and left hand screw-threads, one fitting 

 loosely over the other, so as to make a cylindrical lattice-work 32 cm. (12.6 in.) 

 long. Each coil contained two strands of copper tube 0.3 mm. thick, and weigh- 

 ing 54 grammes to the metre (0.036 pound to the foot). The inner coil bad a 

 diameter of 5.63 cm. (2.22 in.), with nine turns of tube to the strand, the two 

 strands making a length of 319 cm. (10.5 feet) for the coil. The outer coil had 

 a mean diameter of 6.88 cm. (2.71 in.) and a length of 388 cm. (12.7 feet) for tbe 

 two strands. The total length of tbe two coils was, therefore, 707 cm. (23.2 feet), 

 with a beating surface of about 1415 sq. cm. (1.52 sq. ft.) and a total weight of 

 382 grammes (<*.S4 pound). 



Tbe results obtained with this boiler were so far satisfactory as to show that, 

 under the most favorable conditions, when air was supplied in unlimited quanti- 

 ties and there were no disturbing currents to put out or interfere wilb the work 



