Permanent adjustments are same as in the Surveyor’s compass. Focusing the prism: Prism can be slide up or down for focusing to make the readings clear and readable.If the tripod is used, they usually have a ball and socket arrangement for leveling purpose. If it is used as in hand, the graduated disc should swing freely and appears to be completely level in reference to the top edge of the case. Leveling: the instrument has to be leveled if it is used as in hand or mounted over a tripod.Also a plumb-bob is used to judge the accurate centering of instruments over the station. Centering is usually done by adjusting the tripod legs. Centering: it is the process of fixing the compass exactly over the station.Prismatic compass ( Geology Superstore) Major parts of a Prismatic Compass are: The greatest advantage of this compass is both sighting and reading can be done simultaneously without changing the position. It contains a prism which is used for accurate measurement of readings. There are two brass latch hooks (one hook and eye are missing).Prismatic compass is a portable magnetic compass which can be either used as a hand instrument or can be fitted on a tripod. The underside of the case has four brass ball feet. The name presumably belongs to the owner of the case. GALEOTTI"-is stamped in gold on a red rectangle in the center of the lid. The sides of the case and edges of the lid are stamped with gold decorations of flowers and ribbons. The box exterior is covered with green leather that is impressed with parallel lines. The inside of the box lid is upholstered in green velvet tied down with yellow pompoms. The interior of the box is framed in chamois that is now a salmon color. The space below the tray would have held paper. The tabs to lift out the tray are made of red woven ribbon that covers thin strips of leather. The tray is covered with green velvet that is worm eaten. They are different metallurgically as well. The drawing instruments are engraved by different hands and in different styles. This likely held another compass or compass insert. Cursor is held by brass wing nut on steel screw. The slot to hold the case is longer than necessary and likely held additional cases of graphite of differing diameters.īrass with steel points. Ī tubular brass case with a screw-top cover holds the graphite sticks for the pencils. It currently has a jointed, ruling-pen insert with steel blades and brass screw. Long brass extender arm to be inserted into a compass. (13) long extender leg with ruling pen insert The cross-bar of the A is divided into degrees from 0°-90° every 1° and is used with a plumb line to determine the inclination of a surface. The instrument has a sector hinge and opens up into A-frame level with feet. There is a pair of steel blades with brass adjustment screws on each end of a brass handle. There is a knurled screw to tighten it.īrass with one fixed steel point and one removable steel divider-point insert. The steel needle is arrow shaped and has an agate pivot.īrass with one fixed steel point and one removable steel divider-point insert. The magnetic compass has no wind rose and uses the divided circle to indicate bearings in azimuth. ![]() In the center of the circle is the magnetic compass. The protractor is a divided circle marked 0°-180°-0° every 1°. The top of the folding rule is plain, except for a protractor and magnetic compass fixed to the top of the hinge. This side is also stamped, "GOGILLA," which may be a maker's name. The folding rule is divided on the underside into units of Paris feet ("Piede Parigino"), engineering feet ("Piede Inge."), and Tuscan feet ("1/2 Bra-Toscano"), plus an architect's scale ("Palo. (6) folding rule with protractor and magnetic compass ![]() With steel blades fixed in brass handle, and with adjustment screw. For use with smallest dividers in order to make them into a compass.įor tightening the sector hinges and the like For use with smallest dividers in order to make them into a compass. With joint, steel blades, and brass screw. There is a hole in the center of the projection (where the angle lines converge). The protractor is shaped as a triangle with a semicircular opening. These include:ġ) protractor with square and diagonal scale Description This wooden case of drawing instruments holds a lift-out tray that was custom-made for 17 drawing instruments.
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