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Bausch & Lomb 1908 catalog of Engineering Instruments
New 5 inch Mining Transit
with Permanent Prismatic Side Telescope
(Patent Applied For)
The small prism can be thrown in or out of the path of rays of the main telescope, the movement being confined by stops. It is actuated by a small knob from the outside, and a pointer giving the position in which the small prism is exactly in the center of the main telescope; in this position, rays entering the auxiliary objective are reflected into the eyepiece by means of the two prisms. In the described position, the attachment answers as a side telescope.
By moving the small prism against the other stop, the path of the rays in the main telescope becomes unobstructed and the transit telescope can be employed as usual.
Particular attention is called to the fact that no displacement of the object is caused if the prism combination is not absolutely at right angles to the main telescope; on account of the law of double reflection, the parallelism of the rays of the main telescope and those coming through the prism combination, is not affected. It is only necessary to provide a stop in such a manner that the rays passing through the telescope and the attachment lie in one plane and that the small prism is not displaced with reference to the large prism while being shifted. When once adjusted there is little liability of derangement.
The simplicity of this attachment, and the certainty of its working, make it far superior to any side telescope, which latter must be adjusted each time with reference to the main telescope, even in work of ordinary accuracy. For vertical sighting, the main telescope is placed vertically or horizontally, as the large prism can be revolved against two stops which are 90 degrees apart, and if the transit is otherwise in adjustment, the sight through the prism attachment will be truly vertical.
The new mining transits, with prismatic side telescopes, are made in the 5 inch size only. Two styles of vertical circles are offered, and the transits are supplied either with large compass or with U standards having a 3 inch needle, as desired. The prismatic side telescope is permanently fixed in the horizontal axis and is always in adjustment for instant use. One important improvement has been made in the telescope. The focusing is accomplished, from without, by moving a lens system on the inside, thus doing away with the exposed focusing slide, and neither lengthening nor shortening the telescope by sighting for long or short distances. The improved solar attachment is frequently supplied with mining transits, and is admirably suited for use as a top telescope on this instrument, to which it may be attached in the usual manner.
The vertical circle is 5 inches in diameter and reads to single minutes by one double or two opposite verniers as ordered.
The compass needle is 3 7/8 inches in length with the usual standards, 3" with U-standards; mounted upon a center of sapphire.
The erecting telescope is 10 1/2 inches long, has a power of 20 diam., an effective aperture of 1 3/16 inches and an apparent field of view of 30 degrees.
The telescope level is 4 1/2 inches in length, and is graduated in 2 mm. divisions, each division representing 20" of arc.
The plate levels are also graduated in 2 mm. divisions, each division representing 6o" of arc.
The telescope axis carries a center-point which is exactly over the center when the instrument is leveled up and the telescope is horizontal. The axis is also provided with clamp and tangent screw.
The range of the shifting center is 1/2"
Compass and vernier glasses are water tight.
The four German silver leveling screws are provided with dust-caps.
The instrument is 11 1/2 inches in height and weighs approximately 10 lbs.; in carrying case 24 lbs., and when ready for shipment 38 lbs.
The extension tripod weighs 10 lbs., and when packed for shipment 24 1/4 lbs.
|Nick||20||5" Mining Transit, with prismatic side telescope. and as specified. The vertical circle is graduated on the edge as illustrated, and is read by two opposite verniers. The circle guard, compass and vernier glasses are water tight..................||305.00|
|Nickeline||22||Transit, as above, but read by one double vernier, as illustrated on page 19 . . . . . . . . .||295.00|
|Nicotian||24||Transit, as above, but with circle graduated on the surface, as illustrated on page 24, and read by two opposite verniers . . . . .||285.00|
|Nictation||26||Transit, as above, with circle graduated on the surface and read by one double vernier, as illustrated on page 26 ....||275.00|
|Naggy||Gradienter . . . . . . ....||5.00|
|Na bob||Saegmuller Solar Attachment, as described on page 13........||45.00|
|Naiad||Variable Power Eyepiece, in place of regular . .||10.00|
|Nail||Eyepiece Prism, with colored sun-glass .....||6.50|
|Neogen||Fixed Stadias, 1:100 . . . .||3.00|
|Nam||Adjustable Stadias, in place of fixed stadias . .||10.00|
|Nandu||Fixed, but Disappearing Stadias, . . .||5.00|
|Naos||Saegmuller Quick-leveling Head, (see page 12)||10.00|
|Nape||Illuminator for Cross Wires, (a tube with reflector used in place of a sunshade) . . . . . . . .||4.00|
|If a horizontal circle reading to 30" in place of single minutes as regularly furnished is desired, add $10.00.|
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