24 INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 



hand until the neck is twisted sufficiently to prevent the escape of 

 the gas. The rubber bands are then loosened, allowing the neck of 

 the balloon to slip from the nozzle. 



64. For the inflation of the 100-gram balloons, the inflation balance 

 is equipped with an additional filling nozzle, designed to fit the smaller 

 neck of these balloons, and the inflation is accomplished as follows: 



1. Attach the smaller nozzle to the balance. 



2. Bring the balance into the equilibrium position by setting the 

 scale rider on zero of the gram scale. 



3. Place the counterweight (503 gm.) on the left-hand pan beneath 

 the nozzle. 



4. Attach the balloon and fill with gas until the balance is again in 

 equilibrium. 



5. Cut off the flow of gas and remove the balloon from the balance 

 in the usual manner. 



65. It will be noted that the above procedure makes no allowance 

 for the different weights of the balloons. The reason for this lies in 

 the fact that for balloons of tliis weight a variation of a few grams 

 does not materially affect the ascensional rate, provided the same free 

 lift is used in each case. 



66. Wlien helium gas is used for the inflation of balloons, it is 

 necessary to give the balloons greater free lifts than when hydrogen 

 is used in order to obtain the same ascensional rates. This is accom- 

 plished by using heavier counterweights on the balance. The counter- 

 weights used are: 



1. For 30-gram balloons — ascensional rate, 180 meters per minute: 



a. With hydrogen gas, 140 grams. 



b. With helium gas, 154 grams. 



2. For 100-gram balloons — ascensional rate, 280 meters per minute. 



a. With hydrogen gas, 450 grams. 



b. With helium gas, 503 grams. 



67. Fastening neck of balloon. — The neck should be twisted several 

 times and secured by means of three No. 17 rubber bands. The 

 rubber bands are slipped over the twisted portion of the neck and 

 tightly wrapped by a series of alternating half twists and loopings, 

 accompanied by a firm tension to insure a tight joint. If proper care 

 is exercised in this operation, there will be no possibility of leakage 

 of gas through the neck of the balloon. Cord or tape should never 

 be used for tying the neck of balloons. 



68. Danger of explosions. — It is a well-known fact that hydrogen 

 and air when mixed in the proper proportion make a very explosive 

 mixture. Therefore, the following instructions should be adopted 

 and rigidly enforced: 



Smoking should be prohibited at all times in or near the balloon 

 shelter or room where the ballons are being filled or where hydrogen 

 is stored. 



Whenever a balloon during the process of inflation is foimd leaking 

 it should at once be detached from the filling apparatus, taken out- 

 side, and exhausted of hydrogen in the open air. 



In case of a balloon that bursts while being filled, the doors and 

 windows of the shelter, or room used for the purpose, should be opened 

 in order that all of the hydrogen may be driven out by the wind. 



So far as possible, doors and windows of the balloon shelter or room 

 should be kept open each time that the balloon is filled. During 



