. Radiography and the 'X' rays in practice and theory : with constructional manipulatory details . 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
. Radiography and the 'X' rays in practice and theory : with constructional manipulatory details . 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. Fig. 3.—Tube on Stand, Showing Attraction of Cotton Wool. be arranged as in the annexed fig. 3, and underneathit, at a distance of about 6 in., a Franklin plate, or twosheets of writing-paper superimposed, or even sometufts of cotton wool, be placed. If now a discharge beset up in the tube, either by means of a coil giving asuitable length of spark, or else (and preferably) fromthe outer coatings of the Leyden jars belonging to aWimshurst machine, with the discharging balls arrangedat a convenient * striking distance, the tufts of cotton For ordinary tubes this distance will be about 3 in. 18 RADIOGRAPHY wool will be seen to be attracted, the two sheets of paperwill be found to be each charged in opposite senses andtherefore to adhere strongly to one another, or, ihially,the Franklin plate will be found to have taken ii]) acharge. Similar to electricity also, these undulationsor vibrations possess the power of causing certain bodiesto fluoresce or give out light, notably certain sal
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