The electro-magnets are arranged at an angle of 120 deg., and for a
change of current the wheel, r, describes an angle of 60 deg., that is
to say, a sixth of a circumference. The motion of r is transmitted, by
means of the pinion, d, and the wheel, e, to the wheel, T. For a
one-meter variation in level the wheel, T, makes one complete
revolution. It is divided into 100 equal parts, and each arc therefore
corresponds to a difference of one centimeter in the level, and
carries, engraved in projection, the corresponding number. As a
consequence, there is upon the entire circumference a series of
numbers from to 99. The axle upon which the wheel, T, is keyed is
prolonged, on the side opposite e, by a threaded part, a, which
actuates a stylet, g. This latter is held above by a rod, I, which
is connected with a fork movable around a vertical axis, shown in Fig.
6. The rectilinear motion of g is 5 mm. for a variation of one meter
in level. Its total travel is consequently 40 mm. The sheet of paper
upon which the indications are taken, and which is shown of actual
size in Fig.
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