. Machinery and processes of the industrial arts, and apparatus of the exact sciences. Prism Telemeter. prisms are four-sided, the reflecting sides, which are silvered, being at anangle of forty-five degrees to each other, so that a ray which enters at a,after two interior reflections emerges at d, at right angles to its originaldirection. The prisms are inclosed in the boxes marked C, (Fig. 130,) ofwhich they occupy buthalf the height, so that theobserver looking through e. the tubes marked V, cansee an object directly be-fore him through an aper-ture Y on the screen A,while he sees, at the s
. Machinery and processes of the industrial arts, and apparatus of the exact sciences. Prism Telemeter. prisms are four-sided, the reflecting sides, which are silvered, being at anangle of forty-five degrees to each other, so that a ray which enters at a,after two interior reflections emerges at d, at right angles to its originaldirection. The prisms are inclosed in the boxes marked C, (Fig. 130,) ofwhich they occupy buthalf the height, so that theobserver looking through e. the tubes marked V, cansee an object directly be-fore him through an aper-ture Y on the screen A,while he sees, at the sametime,another object situa- Fi£- 131. ted to the right or left, by reflection in the prism, through the aperture 590 PARIS UNIVERSAL EXPOSITION. The two objects thus seen are apparently coincident in direction ? butreally the rays coming from them to the prisms, cross in the interior of theprism (as seen at A, Fig. 131) at right angles to each other. The observ-ing apparatus is hinged to the screen at G, for convenience in , Fig. 130, is a box containing the measuring tape. This instrument was originally constructed in such a manner that inusing it both observers stood facing the distant object. The observeron the left hand kept his position, while the observer on the right moved,at the extremity of the stretched measuring tape between them, untilhis prism was seen by the first observer, in coincidence with the distantobject. The second observer then looking toward the distant object 0, Fig. 132, coin-cident with it, not A,^____-— but some object or point b \——- behind A, as A7. If the FiS- 132- distance A A (suppos- ing A to be in the line 0 A continued) could be accu
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Keywords: ., bookcentury1800, booksubjectmachinery, booksubjectscientificappa
