INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 27 



signaler installed. In order to reduce the volume of sound from the 

 buzzer it is necessary to tap off 20 or 30 turns of wire from one of the 

 buzzer magnet coils and to place them in the circuit. To do this the 

 circuit is broken and one end is soldered to the mounting of the 

 "make and break" device and the other is soldered to the surface at 

 the opposite end of the adjacent coil, as shown in diagram. 



The buzzer switch is incorporated in the plug, the two otherwise 

 unnecessary prongs on the plug are connected together, and the two 

 wires which formerly led to the switch are connected to the indicated 

 posts on the jack. Thus when the plug is inserted in the office 

 station the time signaler is turned on and all is ready for the observer 

 to plug in and start the observation. 



One battery in the circuit consisting of two or three dry cells is 

 all that is necessary. 



76. Releasing balloon. — When all is in readiness for the observa- 

 tion the balloon will be released. The recorder will be provided with 

 Forms No. lllOA-Aer. on a clip board, hard pencil, slide rule, and 

 tuning device. The observer will hold the inflated balloon near the 

 theodolite until the signal of ''read" (or release) is given by the timing 

 device. If the time signaler is used the balloon will be held in readi- 

 ness at the first buzz, and released on the second buzz. The exact 

 time of release to the nearest minute is noted and recorded in the 

 proper space at the top of Form No. 1 llOA-Aer. If a watch is depended 

 upon for time, then the recorder will be forced to watch the time 

 and call out the signals "warning" and "read" as they occur. 



77. A few seconds after the balloon is released the surface wind 

 direction will be determined by pointing the telescope at the balloon 

 and noting the azimuth to the nearest degree. Both the azimuth 

 reading and the direction to the nearest 16 points will be recorded 

 on Form No. lllOA-Aer. 



78. Sighting and jollowing balloon. — As soon as the balloon has 

 moved away from the observation point sufficiently, the observer will 

 sight the telescope upon the balloon by means of the sights on the 

 telescope, then throwing in both tangent screws (not required on 

 "friction drive" type of theodolite), continue to sight the balloon over 

 the telescope tube, while turning the tangent screws or drives to 

 keep the theodolite trained upon the balloon. Note that the object 

 end of the telescope is always inclined toward the left as the observer 

 looks through the eyepiece; that is, the elevation angle must never 

 be greater than 90°. When the rate and character of the motion to 

 keep the balloon in the line of sight have been attained, continue the 

 movement and quickly change the position of the eye to look through 

 the eyepiece. If the rate of movement has been properly judged, 

 the balloon will appear in the field near the intersection of the cross 

 hairs. Thereafter the observer will keep the balloon in the field by 

 suitable movement of the tangent screws or drives. 



79. When the surface wind is very low the elevation angle may be so 

 high that the base plate of the theodolite interferes with the sighting 

 of the balloon with the regular sights. In such cases the high-angle 

 sights, with which all instruments are equipped, must be used. 



80. Fifty-five seconds after the release of the balloon, a signal of 

 "warning" will be given, either by the i recorder or by the time- 

 interval clock. When this signal is given, the observer will bring 

 the intersection of the cross hairs directly over the balloon and keep 



