There are also necessary tools within th'e basket such as a heavy 

 knife for emergency use, and a saw in case the balloon runs afoul 

 of a tree in landing. 



The Navigation of a Balloon — A balloon, like a sail-ljoat, is 

 at the mercy of the wind. Unlike a sail-boat it floats within the 

 current of air and there is no sense of motion. Upon the skil- 

 fulness of the pilot in ascending or descending into air currents 

 of different directions depends successful navigation. He ascends 

 by releasing ballast and descends by releasing gas from the bag. 

 Winds do not blow with like directions at all levels as will be seen 

 from the following table of wind directions and velocities from 

 observations at the U. S. Army Balloon School at Ross Field on 

 a typical morning : 



UPPER AIR DATA FROAI U. S. ARMY BALLOON 

 SCHOOL, ARCADIA, CAL., FEB. 15, 1921 (2). 



Altitude 

 (feet) 



Sur- 

 face 



250 



500 



750 



1000 



1500 



2000 



2500 



3000 



40(i0 



5000 



6000 7000 



8000 



Wind Dir. 



SW 



SE 



E 



E 



E 



SK 



SE 



E 



E 



N 



NW 



NW NW 



NW 



Wind Velo- 

 city (miles 

 per hour) 



3 



4 



5 



6 



8 



11 



12 



12 



12 



6 



16 



35 



46 



64 



It will be observed from a perusal of this table that the wind 

 changes in direction and velocity for eyery level from the surface 

 where the wind is light and from the southwest, 250 feet higher 

 where the wind backed to the southeast, and to 1000 feet altitude 

 where the wind blows from the east with increasing velocity. At 

 1500 and 2000 feet above the earth a southeast wind is again 

 experienced but of 12 miles per hour, which velocity is held 1000 

 feet higher. At 4000 feet altitude the wind is blowing lightly 

 from the north, indicating a transitional region comparable to the 

 "Back-water" of the tides. Although the wind blows steadily 

 from the northwest from 5000 feet up to 8000 feet. The velocity 

 increases proportionately to the distance above the earth's surface, 

 it being 16 miles per hour at 5,000 feet and 64 miles per hour at 

 8,000 feet. To the balloonist, it means that if he wished that 

 morning to fly from Los Angeles to the San Fernando Valley, 

 he must keep his balloon below the 3000 ft. level. If, however, 

 he desires to fly to San Diego, he would throw out sufficient bal- 

 last to enable him to reach the five- to eight-thousand foot level 

 at which latter elevation he would travel to San Diego in about 

 two hours' time. If the balloonist wished to go in an opposite 

 direction, he would keep close to the surface and his progress 

 would be very slow. The movement of the wind in the air Jevels 

 above the earth is not always the same, but varies with the dis- 



2. U. S. Weather Bureau Daily Weatlier Map. Los Angeles, 1921. 



11 



