A. A device for measuring horizontal angles.
Q. Point out the following parts of the instrument:
| 1. | Telescope-tube. |
| 2. | Telescope-trunnion. |
| 3. | Trunnion clamp-screws. |
| 4. | Focusing-knob. |
| 5. | Sunshade. |
| 6. | Dew-cap. |
| 7. | Objective-cell. |
| 8. | Objective. |
| 9. | Eyepiece-adapter. |
| 10. | Eyepiece. |
| 11. | Eye-lens. |
| 12. | Field-lens. |
| 13. | Cross-wire holders. |
| 14. | Cross-wire. |
| 15. | Brashear-Hastings erecting-prism. |
| 16. | Prism-holder. |
| 17. | Prism-cap. |
| 18. | Cross-wire adjusting-screw. |
| 19. | Instrument-base. |
| 20. | Leveling-screws. |
| 21. | Spindle-head. |
| 22. | Worm-gear. |
| 23. | Graduated circle. |
| 24. | Worm-screw. |
| 25. | Worm-box. |
| 26. | Worm-box spring. |
| 27. | Worm-box pivot. |
| 28. | Worm-box adjusting-screws. |
| 29. | Worm-box eccentric-crank. |
| 30. | Index-disk. |
| 31. | Index-pointer. |
| 32. | Disk-crank. |
| 33. | Worm adjusting-screw. |
| 34. | Reading-opening. |
| 35. | Azimuth-clamp. |
| 36. | Azimuth slow-motion screw. |
| 37. | Telescope-yoke. |
| 38. | Yoke-caps. |
| 39. | Levels. |
| 40. | Level-holders. |
| 41. | Level-adjusting screws. |
| 42. | Plumb-bob. |
| 43. | Plumb-bob chain. |
| 44. | Tripod-head. |
| 45. | Tripod-cap. |
| 46. | Tripod-thumbscrew. |
| 47. | Tripod-legs. |
| 48. | Pier-mounts. |
A. See Fig. 58.
Q. Describe how to set the azimuth-instrument up for use.
A. First: Set the graduated circle and index-disc to read the known azimuth of a visible object and clamp (the eccentric-crank being in gear).
Second: Set the eyepiece slightly to the left of the reading-opening and tighten the azimuth-clamp.
Third: Raise the whole instrument by grasping the tripod, and turn it so that the telescope points approximately in the direction of the visible object whose azimuth is known, being careful to set the plumb-bob over the home station at the same time and not destroy the setting of the graduated circle and index-disc.
Fourth: Level the instrument. (This is done by loosening the azimuth-clamp and setting one level parallel to two opposite leveling-screws, then turn these two screws either both inward toward the spindle-head or both outward until the bubble comes in the middle. Perform the like operation with the other two leveling-screws and the instrument is level.)