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VIII.—On the Advantages to be derived from the Use of Metallic Reflectors for Sextants and other Reflecting Instruments; and on Methods of directly determining the Errors in Mirrors and Sun-Shades used in Reflecting Instruments
Published online by Cambridge University Press: 17 January 2013
Extract
It has frequently occurred to me that the difficulty experienced by instrument-makers, in obtaining for sextants and other similar instruments, reflecting mirrors perfectly parallel in their polished surfaces, and also the greater difficulty of procuring glass perfectly homogeneous in its structure, might be overcome by the use of metallic reflectors.
It is well known, that, from the want of perfect parallelism in glass mirrors there arises an error in the reading of such instruments, inasmuch as the emergent ray does not pass out of the glass at the same angle as the incident falls upon it, and that from the want of homogeneousness in the substance, and the unequal refractions caused by the veined structure of the glass.
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- Research Article
- Information
- Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 16 , Issue 1 , 1845 , pp. 61 - 65
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- Copyright © Royal Society of Edinburgh 1845