Ditto, ditto, brass mounted on pillar and claw stand, with elevating rack, 1 eye piece for astronomical purposes, and 1 for land objects, to vary the magnifying power, packed in a mahogany box 12 12 0
The following prices of the same kind of telescope are from the catalogue of Messrs. W. and, S. Jones, 30, Lower Holborn, London.
£ s. d. The improved 2-1/2 feet achromatic refractor, on a brass stand, mahogany tube, with three eye pieces, two magnifying about 40 and 50 times for terrestrial objects, and the other about 75 times for astronomical purposes, in a mahogany case 10 10 0
Ditto, ditto, the tube all brass, with three eye pieces 11 11 0
Ditto, ditto, with vertical and horizontal rack work motions 15 15 0
2. _The 3-1/2 feet Achromatic Telescope._--The object glass of this telescope is from 44 to 46 inches focal length, and 2-3/4 inches diameter. It is generally furnished with four eye-pieces, two for terrestrial and two for celestial objects. The lowest power for land objects is generally about 45, which affords a large field of view, and exhibits the objects with great brilliance. The other terrestrial power is usually from 65 to 70. The astronomical powers are about 80 and 130; but such a telescope should always have another eye-piece, to produce a power of 180 or 200 times, which it will bear with distinctness, in a serene state of the atmosphere, if the object glass be truly achromatic. The _illuminating power_ in this telescope is nearly double that of the 2-1/2 feet telescope, or in the proportion of 7, 56 to 4; and therefore it will bear about double the magnifying power with nearly equal distinctness. This telescope is fitted up in a manner somewhat similar to the former, with a tripod stand which is placed upon a table. Sometimes, however, it is mounted on a long mahogany stand which rests upon the floor, (as in fig. 58.), and is fitted with an equatorial motion; and has generally a small telescope fixed near the eye end of the large tube, called a _finder_, which serves to direct the telescope to a particular object in the heavens when the higher powers are applied. It is likewise eligible that it should have an elevating rack and sliding tubes, for supporting the eye end of the instrument, to keep it steady during astronomical observations, and it would be an advantage, for various purposes which shall be afterwards described, to have fitted to it a _Diagonal Eye Piece_ magnifying 40 times or upwards.