Read A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52

A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52

James Melville Gilliss

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Description:Excerpt from A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by the U. S. Naval Astronomical Expedition to the Southern Hemisphere, During the Years 1849-'50-'51-'52 In order to secure solidity of construction and regular and central expansion of the supports for the pivots and microscope bearers, such form was given to the plug d and to the massive perforated disk 0, that the expansion would act from the center out ward, and therefore be a minimum in its prejudicial effect. Both the disks and the plugs are of red metal and, though separated by thick washers of the same metal, the former are secured to the latter by three strong and equidistant screws. On the suc cessful fastening of the plugs to the pier depends not only the stability of the transit axis, but likewise the immobility of the microscopes, and therefore every precaution was taken to use specially prepared gypsum, and to allow two days for the cement to dry before putting up the disks. Should not the outer faces of the plugs have been placed absolutely parallel, the defect may be remedied by filing down one or more of the washers; otherwise the lines of the microscope bearers will form angles with the planes of the circles. Parallelism of the disks, therefore, is an essential requisite. The Y's, also, and their adjusting screws, are of red metal: One of them may be moved in azimuth, the other in altitude. They are firmly screwed to the disks. To insure that the pivots rest always on the same points of the Y's, on the side of each and next the pier there is a small steel plate, whose upper edge is beveled outwardly. These are held to the Y's by spiral springs, which yield if the axis descend slightly to one side, but are strong enough to press it in place when resting in the counterpoise arms. As the extremities of the pivots are slightly oval, the beveled edges to the plates prevent all possible injury from inadvertent manipulation. To each Y there is also a hinged lever, with a weight at one end, intended to serve as a guide in adjust ment of the pressure of the instrument upon its pivots. The microscope arms are metallic tubes, protected from the sudden in uences of temperature by wooden cases, so contrived as to leave a stratum of air between the tube and wood, and not to cramp the former should the wood warp. They are attached to the dovetailed periphery of the disks by pinching screws, and may be placed at any angles around the circles simply by loosening the screws. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."We have made it easy for you to find a PDF Ebooks without any digging. And by having access to our ebooks online or by storing it on your computer, you have convenient answers with A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52. To get started finding A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52, you are right to find our website which has a comprehensive collection of manuals listed.
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Description: Excerpt from A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by the U. S. Naval Astronomical Expedition to the Southern Hemisphere, During the Years 1849-'50-'51-'52 In order to secure solidity of construction and regular and central expansion of the supports for the pivots and microscope bearers, such form was given to the plug d and to the massive perforated disk 0, that the expansion would act from the center out ward, and therefore be a minimum in its prejudicial effect. Both the disks and the plugs are of red metal and, though separated by thick washers of the same metal, the former are secured to the latter by three strong and equidistant screws. On the suc cessful fastening of the plugs to the pier depends not only the stability of the transit axis, but likewise the immobility of the microscopes, and therefore every precaution was taken to use specially prepared gypsum, and to allow two days for the cement to dry before putting up the disks. Should not the outer faces of the plugs have been placed absolutely parallel, the defect may be remedied by filing down one or more of the washers; otherwise the lines of the microscope bearers will form angles with the planes of the circles. Parallelism of the disks, therefore, is an essential requisite. The Y's, also, and their adjusting screws, are of red metal: One of them may be moved in azimuth, the other in altitude. They are firmly screwed to the disks. To insure that the pivots rest always on the same points of the Y's, on the side of each and next the pier there is a small steel plate, whose upper edge is beveled outwardly. These are held to the Y's by spiral springs, which yield if the axis descend slightly to one side, but are strong enough to press it in place when resting in the counterpoise arms. As the extremities of the pivots are slightly oval, the beveled edges to the plates prevent all possible injury from inadvertent manipulation. To each Y there is also a hinged lever, with a weight at one end, intended to serve as a guide in adjust ment of the pressure of the instrument upon its pivots. The microscope arms are metallic tubes, protected from the sudden in uences of temperature by wooden cases, so contrived as to leave a stratum of air between the tube and wood, and not to cramp the former should the wood warp. They are attached to the dovetailed periphery of the disks by pinching screws, and may be placed at any angles around the circles simply by loosening the screws. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."We have made it easy for you to find a PDF Ebooks without any digging. And by having access to our ebooks online or by storing it on your computer, you have convenient answers with A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52. To get started finding A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52, you are right to find our website which has a comprehensive collection of manuals listed.
Our library is the biggest of these that have literally hundreds of thousands of different products represented.

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A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52

A Catalogue of 16, 748 Southern Stars, Vol. 9: Deduced by the United States Naval Observatory From the Zone Observations Made at Santiago De Chile, by ... Hemisphere, During the Years 1849-'50-'51-'52

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