Orientation Instrument.
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Description
Image from page 179 of "Transactions" (1852)
Identifier: transactions53nort Title: https://www.flickr.com/photos/internetarchivebookimages/tags/bookidtransactions53nort">Transactions Year: https://www.flickr.com/photos/internetarchivebookimages/tags/bookyear1852">1852 (https://www.flickr.com/photos/internetarchivebookimages/tags/bookdecade1850">1850s) Authors: https://www.flickr.com/photos/internetarchivebookimages/tags/bookauthorNorth_of_England_Institute_of_Mining_and_Mechanical_Engineers__Newcastle_upon_Tyne">North of England Institute of Mining and Mechanical Engineers, Newcastle-upon-Tyne https://www.flickr.com/photos/internetarchivebookimages/tags/bookauthorNorth_of_England_Institute_of_Mining_and_Mechanical_Engineers__Newcastle_upon_Tyne__Report_of_the_Committee_upon_mechanical_coalcutting__1905">North of England Institute of Mining and Mechanical Engineers, Newcastle-upon-Tyne. Report of the Committee upon mechanical coalcutting, 1905 Subjects: https://www.flickr.com/photos/internetarchivebookimages/tags/booksubjectMineral_industries">Mineral industries https://www.flickr.com/photos/internetarchivebookimages/tags/booksubjectMechanical_engineering">Mechanical engineering Publisher: https://www.flickr.com/photos/internetarchivebookimages/tags/bookpublisherNewcastle_upon_Tyne">Newcastle-upon-Tyne Contributing Library: https://www.flickr.com/photos/internetarchivebookimages/tags/bookcontributorGerstein___University_of_Toronto">Gerstein - University of Toronto Digitizing Sponsor: https://www.flickr.com/photos/internetarchivebookimages/tags/booksponsorUniversity_of_Toronto">University of Toronto View Book Page: https://archive.org/stream/transactions53nort/transactions53nort#page/n179/mode/1up" rel="noreferrer nofollow">Book Viewer About This Book: https://archive.org/details/transactions53nort" rel="noreferrer nofollow">Catalog Entry View All Images: https://www.flickr.com/photos/internetarchivebookimages/tags/bookidtransactions53nort">All Images From Book Click here to https://archive.org/stream/transactions53nort/transactions53nort#page/n179/mode/1up" rel="noreferrer nofollow">view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: take time, andmight lead to a derange-ment of the line of colli-mation. He therefore ap-pended an exact descriptionof the mode of use of theinstrument. The orienta-tion instrument, shown inFjg. 1, is specially dis-tinguished from othertypes of instruments witha declination-needle, bythe fact that the coin-cidence of the north-southlines with the axis ofcollimation can be directlytested from time to timeby means of the telescope,and this constitutes itsspecial feature. The caseof the compass-needle restsupon a support that can beadjusted in all directions, and the former can be readily removed inorder to clean the magnetic needle. By a suitable device, it issecured in an exactly true concentric and diametral position afterbeing replaced. The magnetic needle is also arranged for revers-ing. According to the size of the instrument, the needle has a * Trans. Inst. M.E., 1902, vol. xxiii., page T>7.~>. f Ibid., 1902, vol. xxiii., page 598. % This is, however, by no means necessary . Text Appearing After Image: Fig. 1. Orientation Instrument. DISCISSION —MIXK-M RVEYIX<. IXsl IUMKX IS. 1 58 length of <J to (S inches (15 to JO centimetres), tin1 diameter of thelimb of the horizontal circle being always equal to the length ofthe compass-needle. This needle is beam-shaped, and at bothends fine lines are engraved on it (Fig. 2) by means of a diamond.The cap consists of a highly-polished garnet or ruby. The remov-able front lens is only employed for the adjustment of the com-pass-needle; and during other observations it is not used, butremains in the box. After the instrument has been adjusted, measurements aremade as follows:—The zero of the vernier is first set to the zeroof the horizontal limb ; then the body-piece of the instrumentis turned until the magnetic needle swings freely; by means ofa hand-lens the needle is thenset in the magnetic meridian by ran-causing the fine line, a, of themagnetic needle to coincide exactlywith an equally tine line, b, en- graved on the side of the co Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work. -
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Link: https://www.flickr.com/photos/126377022@N07/14765582152/
Resource type: Image
Added by: Simon Cotterill
Last modified: 3 years, 11 months ago
Viewed: 394 times
Picture Taken: 1852-01-01T00:00:00 -
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