Fig. 281.—Bellamy's road tracer.
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This instrument has been improved by Mr. C. V. Bellamy, M.I.C.E., M.I.M.E., F.G.S., &c., Director of Public Works, Lagos, West Africa, a civil engineer who has had great experience in the colonies, and it will be found much more accurate, less liable to get out of order and far more convenient to use than the old forms. It is shown at Fig. 281.
The chief feature of this pattern lies in the adoption of the arc of a circle instead of a straight scale, and a pendulum weight actuated by a rack and pinion in place of the screw and sliding weight. This admits of greater nicety in the divisions and allows a stronger and lighter construction.
The sighting tube is provided with reversible sliding shutters, so that back readings may be taken without unclamping the instrument or altering the vernier or index. A powerful clamp is provided for locking at any desired grade.
A recent further improvement by Mr. Bellamy has been made by making this instrument in a form to give readings in degrees of arc as well as in gradients. Fig. 282.
Fig. 282.—Bellamy's improved road tracer.
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