A N I 



Short historical notice : 



October 15, 1783. M. Pilatre de Rozier was the first person who ever 

 ascended in a balloon ; it was inflated with heated air. He perished in a 

 subsequent ascent, being the first who did so. 



December 1st, 1783. M. M. Roberts and Charles first ascended with an 

 hydrogen gas balloon. 



September 15th, 1784?. The first aerial voyage in England performed 

 by Lunardi. 



Jan. 7, 1785. M. Blanchard and Dr Jeffries passed from Dover to Calais. 



August, 1785. Blanchard in one of his excursions from Lisle, traver- 

 sed a distance of more than 300 miles without halting. 



Sept. 21, 1802. Garnerin first descended in a parachute from London. 



September 15, 1804. Gay Lussac ascended from Paris for scientific 

 purposes, and rose to the enormous height of 22,912 feet ; or 23,040, i. e. 

 more than 4J miles above the level of the sea ; being 1600 feet above the 

 summit of the Andes ; the barometer sunk to 12,95 inches. From this 

 last ascent two results were obtained; (1) that the intensity of the mag- 

 netic power continues the same at all accessible distances from the earth's 

 surface : and (2) that the proportions of oxygen and nitrogen, which 

 constitute the atmosphere, do not vary sensibly in the most extended 

 limits. 



AIR Atmospheric. See Atmosphere. 



AIR Pump. See Pump. 



ANGULAR Velocity. See Central Forces. 



ANIMAL Strength. (Playfair.) 



1. The strength of men, and of all animals, is most powerful when di- 

 rected against a resistance that is at rest : when the resistance is over- 

 come, and when the animal is in motion, its force is diminished ; lastly, 

 with a certain velocity the animal can do no work, and can only keep 

 up the motion of its own body. 



2. A formula, having the three properties just mentioned, will afford 

 an approximation to the law of animal force. Let P be the weight which 

 the animal exerting itself to the utmost, or at a dead pull, is just able to 

 overcome, W any other weight with which it is actually loaded, and v 

 the velocity with which it moves when so loaded ; c the velocity at which 

 the power of drawing or carrying a load entirely ceases ; then, till ex- 

 perience has led to a more accurate result, we may suppose the strength 

 of animals to follow the law expressed by the formula 



Tliis is Euler's Formula. 



