Astronomy and Astro-Physics Volume 10

Astronomy and Astro-Physics Volume 10

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 edition. Excerpt: ...the cylinder is rotated. The bottom of the box is hinged, so that the cylinder can be removed in order to allow the second slit to be observed with a positive eye-piece passing through the back of the box. This slit can be opened or closed by turning a head at the side of the box, and by means of a slide passing before the slit the box can be closed and removed from the spectroscope without danger of exposing the film to the light. A means of producing a slow and uniform motion is the other requisite of the method, and a modified form of clepsydra is attached to the observing telescope for this purpose. A well packed piston slides in a smoothly bored and polished brass cylinder, the piston-rod passing through stuffing boxes in each head. The cylinder is filled with a mixture of equal parts of glycerine and water, and by the motion of the piston this fluid is forced through a small brass tube connecting the two ends of the cylinder. A valve in the center of the tube regulates the rate of flow, and this is controlled by a pointer moving over a divided arc. A ten pound weight is attached to one end of the piston-rod by a flexible cord of braided wires, and the other end of the rod is connected with the pulley on the axis of the rotating filmcarrier by means of a silk cord. A small "snap rubber" passes around the pulley in the opposite direction, and supplies the necessary tension. It has been found that below a certain speed the motion of the small clepsydra used cannot be relied upon as being entirely uniform, so that it is advantageous in the case of a very slow drift of the sun across the slit, to attach an arm about ten inches long in place of the pulley on the axis of the film-cylinder. The thread from the end of the piston-rod more

Product details

  • Paperback | 190 pages
  • 189 x 246 x 10mm | 349g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236649435
  • 9781236649430