NO. 8 SAMUEL PIERPONT LANGLEY — ABBOT 39 



table revolutions was less than this for the higher velocities, so that 

 the highest attained in the experiments did not reach this upper limit, 

 but was a little over loo feet (30 meters) per second, or about seventy 

 miles per hour. The precise velocity actually attained by the turn- 

 table is determined, quite independently of the speed of the engine, 

 by an electrical registration on the standard chronograph in the 

 observatory." 



Langley devised ingenious recording instruments called the " sus- 

 pended plane," the " resultant pressure recorder," the " plane drop- 

 per," the " component pressure recorder," the " dynamometer chrono- 

 graph," the " counterpoised eccentric plane," and the " rolling car- 

 riage," all illustrated in the paper under discussion, and with these 

 made many experiments. 



" The most important general inference from these experiments, as 

 a whole, is that, so far as the mere power to sustain heavy bodies in 

 the air by mechanical flight goes, siicJi mechanical flight is possible zvith 

 engines we nozv possess, since effective steam-engines have lately been 

 built weighing less than 10 pounds to one horse-power, and the experi- 

 ments show that if we multiply the small planes which have been 

 actually used, or assume a larger plane to have approximately the 

 properties of similar small ones, one horse-power rightly applied, can 

 sustain over 200 pounds in the air at a horizontal velocity of over 

 20 meters per second (about 45 miles an hour), and still more at still 

 higher velocities. These numerical values are contained in the fol- 

 lowing table, repeated from p. 66. It is scarcely necessary to observe 

 that the planes have been designedly loaded, till they weighed 500 

 grammes each, and that such a system, if used for actual flight, need 

 weigh but a small fraction of this amount, leaving the rest of the sus- 

 tainable weight indicated, disposable for engines and other purposes. 

 I have found in experiment that surfaces approximately plane and of 

 i/io this weight are sufficiently strong for all necessary purposes of 

 support. 



" Data for soaring of 30 X 4-8 inch planes ; weight, 500 grammes 



