54 A MANUAL FOR NORTHERN WOODSMEN 
the telescope to a horizontal position; five chains north of the 
place of observation set a stone or drive a firm peg, upon which 
by a strongly illuminated pencil or other slender object, exactly 
coincident with the vertical wire, mark a point and drive a tack 
in the line of sight thus determined; then, to eliminate possible 
errors of collimation or imperfect vertically of the motion of the 
telescope, quickly revolve the vernier plate 180°, direct the glass 
at Polaris and repeat the observation; if it gives a different result 
find and mark the middle point between the two results. This 
middle point, with the point marked by the plumb bob of the 
transit, will define the trace of the vertical plane through Polaris 
at its eastern or western elongation, as the case may be. 
By daylight lay off to the east or west, as the case may require, 
the proper azimuth taken from the following table (page 56); the 
instrument will then define the meridian. The needle may be 
read then, giving the magnetic declination, east or west as the case 
may be. Or the fine may be permanently marked for reference 
at another time or with another instrument. 
To Determine a Meridian without a Telescope 
Attach a plumb line to a support situated as far above the 
ground as practicable, such as the limb of a tree, a piece of board 
nailed or otherwise fastened to a telegraph pole, a house, barn, 
or other building, affording a clear view north and south. 
The plumb bob may consist of some weighty material, such as 
a brick, a piece of iron or stone, weighing four to five pounds, 
which will hold the plumb line vertical, fully as well as one of 
finished metal. 
Strongly illuminate the plumb line just below its support by a 
lamp or candle, care being taken to obscure the source of light 
from the view of the observer by a screen. 
For a peep sight, cut a slot about one-sixteenth of an inch wide 
in a thin piece of board, or nail two strips of tin, with straight 
edges, to a square block of wood, so arranged that they will stand 
vertical when the block is placed flat on its base upon a smooth 
horizontal rest, which will be placed at a convenient height south 
of the plumb line and firmly secured in an east and west direction, 
in such a position that, when viewed through the peep sight, Po¬ 
laris will appear about a foot below the support of the plumb line. 
The position may be practically determined by trial the night 
preceding that set for the observation. 
About thirty minutes before the time of elongation, as obtained 
from the table, bring the peep sight into the same line of sight with 
the plumb line and Polaris. 
To reach elongation, the star will move off the plumb line to 
the east for eastern elongation, or to the west for western elonga¬ 
tion; therefore by moving the peep sight in the proper direction, 
east or west, as the case may be, keep the star on the plumb line 
until it appears to remain stationary, thus indicating that it has 
reached its point of elongation. 
