82 A MANUAL FOR NORTHERN WOODSMEN 



and read the final angle. If the instrument has two ver- 

 niers both should be read. It is customary to record the 

 reading after turning the angle once, as a check on 

 the repeated reading. The true reading is the average of 

 the values obtained for the angle with telescope direct 

 and telescope inverted. 



To Prolong a Straight Line. Set up the instrument over 

 the forward point and sight the telescope on. the rear one. 

 Set both clamps, revolve the telescope on its axis, and set a 

 new point as far ahead as convenient or desired. 



More Accurately. With the telescope in its natural 

 position, turn on the rear point, clamp, revolve the tele- 

 scope as above, and set a stake and tack at the forward 

 pointing. Then, leaving the telescope inverted as it is, 

 swing the plates around half a circle and set on the rear 

 point again. Revolve the telescope, and again sight at 

 the forward point. If the two pointings ahead do not 

 coincide, set a tack half-way between the two and it will 

 be in the line desired. 



To Measure a Vertical Angle. For this purpose the ver- 

 tical circle must be adjusted so as to read zero when the 

 telescope is level, or, if it is not adjustable, the error of its 

 reading must be obtained, as explained under adjustments 

 of the transit. Then the angle of elevation or depression 

 to any point may be measured by sighting the telescope 

 upon it and reading the vertical angle by means of the 

 vertical circle and its vernier. 



To Survey a Piece of Ground with the Transit. Set 

 up on the initial point of the survey, turn to the second 

 point, read the bearing of the line, recording it for a check 

 on later angles, and measure the line. Set up over the 

 second point, set the two plates to read zero, and clamp 

 them together; then turn the telescope at a rod held ver- 

 tical and carefully centered over the first point. Set the 

 lower clamp and loosen the upper one, swing the tele- 

 scope with the upper plate around until the third point is 

 sighted, and read the angle so turned. Head the bearing 

 for a check, and measure the line. Proceed in this way 

 until all the angles have been turned and all the sides 

 measured. Interior angles should always be read, though 



