File:Radiography and the 'X' rays in practice and theory - with constructional manipulatory details (1898) (14754877371).jpg

Identifier: radiographyxrays00bott (find matches)
Title: Radiography and the 'X' rays in practice and theory : with constructional manipulatory details
Year: 1898 (1890s)
Authors: Bottone, Selimo Romeo
Subjects: Electric radiation X-rays X-Rays Radiography
Publisher: London New York : Whittaker & Co.
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
sely as the pressure between 11 in. of mercuryand 30 in. (which is equal to the pressure of one atmos-phere). At lower pressures a greater difference ofpotential must be used to produce a spark. When wecome to an exhaustion equal to about tuu^ott of anatmosphere, theE.M.F. required to produce a dischargeis very nearly half as much again as that requiredunder ordinary atmospheric conditions. § 7. When such high vacua are reached, the electricdischarge produces httle or no visible light; but itspresence is capable of being rendered evident by itspower of causing certain bodies to glow with light, or fluoresce. If the apparatus take the form of a glass 16 hAhTOGRAPHY tuU ov Imll) isio li^. 2) with a Ilaliiiuiii electrodeat each end, as the glass itself is a body capable of* fluorescing;, the interior of the bulb is seen to glowwitli a soft yellowish light, which may vary accordingto the degree of vacuum in the tube and the voltage ofthe current, passing from a pale apple-green to a dis-
Text Appearing After Image:
Fio. 2.— Crookes Tube (Oli» Form). tinct canary-yellow colour. In any case, however, thelight is so feeble as to be barely perceptible in day-light. § 8. Whatever may be the nature of the vibration Usually designated a Crookes tube, from the name of thescientist who first investigated the properties of these high vacua. VACUUM ON ELECTRICAL DISCHARGES 17 or undulation set up in the highly rarefied mediumcontained in the exhausted tube, what is certain is, thatit possesses properties which partake at once of those oflight and of electricity, while differing in many respectsfrom both. One of the properties common to electricityis that of setting up inductive effects in surroundingmedia, and of attracting light bodies placed in thevicinity of the exhausted tube wherein the discharge istaking place. These effects may be easily shown if a tube

Note About Images