38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



Steadily and securely guided through the air, or safely brought to the 

 ground without shock, or even that the plane itself is the best form 

 of surface for support ; all these are practical considerations of quite 

 another order, belonging to the yet inchoate art of constructing suit- 

 able mechanisms for guiding heavy bodies through the air on the 

 principles indicated, and which art (to refer to it by some title dis- 

 tinct from any associated with ballooning) I will provisionally call 

 aerodromics." With respect to this inchoate art, I desire to be under- 

 stood as not here offering any direct evidence, or expressing any opin- 

 ion other than may be implied in the very description of these experi- 

 ments themselves. 



" The experiments in question, for obtaining first approximations 

 to the power and velocities needed to sustain in the air such heavy 

 inclined planes or other models in rapid movement, have been prin- 

 cipally made with a very large whirling table, located on the grounds 

 of the Allegheny Observatory, Allegheny, Pa. (lat. 40°27'4i.6" ; long. 

 5'^20™2.93® ; height above the sea-level, 1,145 feet) . 



" The site is a hill on the north of the valley of the Ohio and 

 rising about 400 feet above it. At the time of these observations the 

 hill-top was bare of trees and of buildings, except those of the obser- 

 vatory itself 



" The whirling table consists essentially of two symmetrical wooden 

 arms, each 30 feet (9.15 meters) long, revolving in a plane eight feet 

 above the ground The whirling table was driven first by a gas- 

 engine of about 1 1 horse-power, but it was found inadequate to do the 

 work required, and, after October 20, 1888, a steam-engine giving 10 

 horse-power was used in its stead 



" This system gives for 120 revolutions of the steam-engine per 

 minute, driving — 



18 in. pulley, 48 revolutions of turn-table per minute = 100 + miles per hour 

 at end of arm. 



25^ in. pulley, 24 revolutions of turn-table per minute = 50 + miles per hours 

 at end of arm. 



36 in. pulley, 12 revolutions of turn-table per minute = 25 -f miles per hour 

 at end of arm. 



" By regulating the speed of the engine any intermediate velocities 

 can be obtained, and thus the equipment should be susceptible of 

 furnishing speeds from 10 to 100 miles per hour (4.5 to 45 meters 

 per second) ; but owing to the slipping of belts the number of turn- 



" From aepoSpofieu, to traverse the air ; aepodpotios, an air-runner. 



