6 INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 



Figure 2.— Theodolite used in balloon work (B, back of instrument; BA, bubble adjustment screw; BP, 

 base plate: C, cap or cover block; CR, clamp ring; CH", back counterweight; civ, front counterweight; E, 

 eyepiece; f. focusing screw; F, front of instrument; J[, carrying ring;. H.4, horizontal axis; HC, horizontal 

 circle; hi', horizontal limb and right or 45° vernier; IIV, horizontal limb and front vernier; IIT, horizontal 

 tangent screw; L, leveling clamp screw; LS. leveling screws; p, plumb bob hook; P, plate clamp screw; 

 /'/-, plate level or bubble; PH, prism housing; RS, reticle screws; S, shifting center; SL, standard level or 

 bubble; SS. sun shade; ST", shifting center tension; T, tripod head; TS. telescope stop; VA, vertical axis: 

 ^'C, vertical circle; KT, vertical limb and vernier: VT, vertical tangent screw; Y. yoke standard). 



