In adjusting a surveyor's level, see that the two plates are parallel, with the screw points touching the lower plate. Open the legs to an angle of, say, 30o. Stand between two of the legs and grasp the head of the legs with the left hand. With the right hand place the telescope at right angles to the direction of the leg on your right and move the leg to or from you to bring the bubble central. Then, still grasping the head of the legs with the left hand, with the right hand place the telescope at right angles to its former position - that is, in line with the leg on the right. Move the leg in or out to bring the bubble central in this direction. Then press the legs down firmly and remove the left hand. Now place the telescope over two diagonally opposite screws; turn both at the same time, moviug the thumbs inward to bring the bubble to the right, or moving them outward to bring the bubble to the left, and leave it central. Then place the telescope over the other two screws, and bring the bubble central in the same way.

The bubble should now remain central in any position of the telescope, Turn the eyepiece clockwise while drawing it in or out until the cross wires can be distinctly seen, then direct the telescope to the staff and focus the object glass by the milled head at the side of the telescope to show the figures clearly. The reading is now taken by the apparent position of the horizontal wire. The two vertical wires enable the surveyor to see when the staff is upright in the direction of the line of vision. The stall is kept in such a position by the skill of the staff-holder, or is slowly waved to or from the surveyor so that he may take the lowest reading at the time the staff will be upright. Two additional horizontal wires may be so placed that they will show, say, 1ft. on the staff at a distance of 100 ft.; the difference of reading at the upper and lower wires will then be the approximate distance. For example, 3.47 - 215 = a distance of 132 ft.