The Cincinnati Medical Advance 1875 Vol 2 Classic Reprint

Author : J. a Thacker
Publisher : Forgotten Books
ISBN 13 : 9780267390991
Total Pages : 104 pages
Book Rating : 4.3/5 (99 download)

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Download or read book The Cincinnati Medical News, Vol. 12 written by J. a Thacker and published by Forgotten Books. This book was released on 2018-01-31 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from The Cincinnati Medical News, Vol. 12: March, 1879 Mr. Mayall said: The advance, then, that has been made in the utilization of larger apertures amounts to this: That, whereas, with the dry lens on a balsamed object we are absolutely limited to an aperture less than eighty two degrees, measured in the body of the front lens. This limit is proved by the diagrams I have shown you of the maximum angle that can be computed for a lens to have a front focus in air. It is also proved by a consider ation of the angle of the image rays, as they are radiated from the object itself in balsam; for, although this angle of image rays, viewed as nascent from a self-luminous object capable of scattering rays in all directions, may be 180 degrees in the substance of the balsam and cover glass, of this 180 degrees only eighty-two degrees of the central portion can emerge into air - all the rays beyond this limit are internally reflected at the cover-glass. This cone of eighty-two degrees becomes 180 degrees in air, and a large part must necessarily be lost by reflexion at the first incidence on the plane front of the lens. But, with a formula permitting the use of water medium be tween the front lens and the cover-glass, the aperture of the image rays may reach 126 degrees - double the criti cal angle from glass to water; and, with oil medium, the aperture is limited only by the form of front lens that can be constructed by theoptician, as demonstrated by Professor Stokes in his recent communication on the 'theoretical Limit of Aperture, ' at'the Royal Microscopi cal Society. 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.