Proceedings of the Royal Irish Academy Volume 6 - Softcover

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1858 Excerpt: ...a Torricellian vacuum within, through which, by bringing the sliding rod of the receiver in contact with the platinum wire, discharges can be made. A hole 0i-2 diameter, and l'-O long, is drilled in the apex of the cast-iron core, by inserting in which a miniature jar of quilltube, filled with a known bulk of any gas, before applying the covering disc, this will escape when the bell-glass rises, and thus enable one to experiment in a vacuum of that gas at any required attenuation. "With respect to the next in interest of these facts, the existence of the luminous menisci, I am unable to form an opinion as to whether the differences which I have mentioned arise from specific qualities of the gases, or merely from the degree of density. The decided manifestation of them in hydrogen would seem to imply the latter. If so, air at 0.06 should show the same as I have described for hydrogen at 0-85 and at 0005, as the other at 0-07. The latter exhaustion will require a better pump than mine to try it: but in the first the hydrogen shows the phenomena far more distinct than the air, and the same thing is true of carbonic acid, notwithstanding its high specific gravity. "My present notion of these menisci and their divisions is, that they are surfaces of interference. The fact of their being produced by a single discharge shows that they do not depend on the discontinuity of the current (unless, indeed, that single discharges may be a succession of waves); and the absence of the negative blue light seems equally to show that they do not result from zones of alternating electric condition in the medium. "The colour is related to the nature of the medium; but the rotation of the positive portion of the light, the quiescence of the negative, and its invar...