Gurley manual of surveying instruments .. by Gurley W. & L.E. Troy N.Y

Author:Gurley, W. & L.E., Troy, N.Y. [from old catalog]
Language: eng
Format: epub
Tags: Surveying
Publisher: Troy, N.Y., W. & L.E. Gurley
Published: 1855-03-25T05:00:00+00:00

The first form of this instrument, and that which is most com* nonly used by the government surveyor, is shown in fig, 16, and still better in the engraving at tho opening of this artida

As there seen, the main plate which carries the sights, &c., is but a trifle larger than the circular one on which the solar work is placed.

The solar apparatus, which is of the usual form and size, is permanently attached to the sockets of the instrument by a screw, the head of which may be seen in the inside of the pocket when the instrument is removed from the ball.

The Sockets are very strong, and the.whole instrument is exceedingly compact, light, and substantial.

The Tangent Movement between the plates is partly shown in the figure, the clamp screw, however, is concealed.

The Clamp Screw, by which the instrument is fastened to the spindle, is shown on the side of the socket.

The Spring Catch, of which the knob is shown opposite the head of the clamp screw, prevents the instrument from falling from the spindle when carried on the shoulder, without being previously clamped. ^

The lines of refraction are shown on one of the sights, but as we have* previously remarked, are very seldom used in practice.

The Tangent Scale for angles of elevation and depression is also seen upon the sights, and is sometimes of service in reducing an inclined to a horizontal surface in chaining.

The Graduations of this instrument are made upon silver plate, and figured as usual, the arcs and circles being read to single minutes by their respective verniers.

The Solar Apparatus has the same adjustments and appliances as have been previously described.

This form of the Solar Compass is generally used upon the adjusting socket shown in fig. 14, but may also be placed »pon the leveling tripod if desired.

Digitized by VjOOQIC

THE SDLAE TELESCOPE COMPASS.

In this, the second form of onr improved Solar Compass, the solar apparatus and the arrangement of the socket, &c^ is precisely like that of the instrument just described.

The main or lower plate, however, is now made circular, the sights being dispensed with, and a telescope substituted in their stead.

The telescope is from ten to twelve inches long, furnished with cross wires, &c., and turns by its projecting spindle within a socket attached to the lower plate of the instrument, so as to revolve in either direction, as in taking fore and back sights, or to run lines up or down steep ascents or descents, with the same ease as that of the ordinary Transit.

Attached to the ball of the telescope, and turning with it, is also shown an index, with vernier reading to five minutes, which moving over a graduated circle, enables the surveyor to take angles of elevation and depression with great faciUty.

The telescope is also furnished with the micrometer wires already described, the movable wire being adjusted by the small screw heads shown above and below to one side of those which effect the ordinary adjustment of the wires.

The socket

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