10 INSTRUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 



turns of the spring for equalizing the adjustment of the leveling 

 screws. (If the instrument is of the type which has the screw- thread 

 tripod head, it is attached to the tripod by simply screwing it onto 

 the threaded tripod head.) The theodolite is now completely as- 

 sembled and, after adjustment and checking, will be ready for observa- 

 tion work. 



19. Packing the theodolite. — Whenever it becomes necessary to ship 

 the theodolite, a great deal of care must be given to the packing and 

 preparation for shipment. The packing cases in which the instru- 

 ment and tripod are received should be preserved for this purpose. 

 If the style of case used necessitates the separation of the telescope 

 from the standard and base plate, the preparation of the instrument 

 for packing is accomplished by reversing the instructions given in the 

 paragraphs under "Assembling the theodolite." In addition (on the 

 type having a screw-thread drive), the horizontal tangent screw, HT, 

 figure 2, is to be thrown into mesh with the base plate, BP, and secured 

 there by wrapping and tying a short length of string about the hori- 

 zontal tangent screw, HT, and the telescope stop, TS. The vertical 

 tangent screw, VT, should be disengaged and the base clamp, P, 

 loosened. Place the assembled standard and base plate, which has 

 been secured to the auxiliary shelf for that purpose, in the bottom of 

 the case so that the right horizontal vernier, HV, is about midway 

 and toward the front of the case. With the older type of instrument 

 the telescope, with sunshade and eyepiece, is then laid in its supporting 

 rack and placed in the upper part of the shipping case, with a piece of 

 folded paper inserted between the telescope tube and the stay blocks 

 on the underside of the top of the packing case. After closing and 

 locking the door, fasten the key securely to the case. Each theodolite 

 should be packed in its own case; that is, the case bearing the same 

 serial number. The shipping case containing the theodolite must be 

 substantially crated before shipment. 



20. Care oj the theodolite. — The theodolite, being a delicate and 

 costly instrument, should be given particular care and attention. It 

 should never be left standing without the assurance (1) that the instru- 

 ment is securely fastened on the tripod; (2) that the tripod is well 

 opened; (3) that the legs are firmly planted to prevent slipping — a 

 slight pressure of the foot upon the projecting plate of the tip of the 

 tripod leg will accomplish this; and (4) that on windy days the theo- 

 dolite should not be left standing unless there is some means of 

 securing it to the surface. All instruments purchased during the past 

 few years have tripods equipped with anchor rods, or chains, for that 

 purpose. Those not so equipped may be fastened by means of ordi- 

 nary screen-door hooks and eyes. The hooks are fastened to the 

 (inner) side of the tripod legs, near the bottom, and the eyes are 

 screwed into the platform. A theodolite should always be fastened 

 by one of these methods whenever it is left standing alone. When 

 left standing between observations the instrument should also be 

 protected from dust and weather by covering with the special cover 

 furnished by the central office for that purpose. Should it become 

 necessary to remove dust or moisture from the object lens, only a 

 clean, dry chamois or soft cloth should be used. In case the lens cap 

 is removed, care should be taken that it is screwed firmly in place 

 again. On instruments having the screw-thread type of drive, 

 special attention should be given to the tangent screws of both the 



