CONTENTS 



Page 



Introduction 1 



I. Station and observations points 2 



II. Theodolites 5 



III. Pilot Balloons 20 



IV. The Observation 25 



V. Forms and reduction tables 41 



VI, Two-theodolite observations . 47 



VII. The tail method 58 



Index , 67 



LIST OF ILLUSTRATIONS 



Pilot balloon observations Frontispiece 



Figure 1. Section of observation platform 4 



Figure 2. Theodolite used in balloon work 6 



Figure 3. Theodolite vernier 7 



Figure 4. Section of theodolite showing arrangement of verniers 8 



Figure 5. Collimation adjustment 11 



Figure 6. Effect of prism on line of sight 12 



Figure 7. Horizontal axis adjustment 13 



Figure 8. Peg adjustment 14 



Figure 9. Constellations of Ursa Major and Cassiopeia 17 



Figure 10. Inflation balance for "definite" inflation 23 



Figure 11. Telephone circuit with signaller installed 26 



Figure 12. Graphing board for construction of wind direction and velocity 



graphs on Form No. 1115-Aer 39 



Figure 13. General plan of triangulation for two-theodolite observations-- 49 

 Figure 14. Plan of triangulation for two-theodolite observations when bal- 

 loon is in a vertical plane through the base line 51 



Figure 15. Plan of triangulation for two-theodolite observations when bal- 

 loon is in a vertical plane through the base line and the stations are at 



the same elevation 52 



Figs 16 and 17. Plan of triangulation for two-theodolite observations when 

 the balloon is in a vertical plane through the base line and the stations 



are at different elevations 53 



Figure 18. Plan showing correction to be applied to two-theodolite com- 

 putations to allow for earth's curvature 57 



Figure 19. Plan of triangulation for "tail method" in single-theodolite 



observations 58 



LIST OF TABLES 



Table 1. Pilot balloon ascension report (single- theodolite) , Form No. 



lllOA-Aer 61 



Table 2. Pilot balloon ascension report (two-theodolite) Form No. 1110- 



Aer 62 



Table 3. Rate of ascent, in meters per minute, for weight (w) and free 



lift (1) 63 



Table 4. Degrees Fahrenheit into degrees centigrade 64 



Table 5. Miles per hour into meters per second 65 



Table 6. Inches into millibars 66 



IV 



