Willson, Robert Wheeler, 1853-1922 · Boston, New York Ginn & company · leaf 15
e as a top. (2) A board, 18 inches long and 8 inches broad,furnished with leveling screws and smoothly covered with whitepaper fastened down by (3) thumb tacks. (4) A lecel for levelingthe board, (o) A compass. (6) A glass plate, 6 inches long and2 inches broad, along the median line of which a… … Fig. 2 nearly as possible perpendicular to the length of the board. Placethe board upon the table and level approximately. Put the com-pass on the middle of the pencil line and put the glass plate on thecompass with its central line over the center of the needle; turnthe plate till its median line…
Astronomy
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