Proceedings of the Royal Society of London Volume 44 (Paperback)

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. 1888 edition. Excerpt: ...all the quadruple group near X2802 and the quadruple group beyond, and in one case only, in oxygen, the group near, described below, and the flame-triplet near M. When no jar is used sometimes only X2852 is to be seen, sometimes X2852 and the strong pair neat X2802, and sometimes also the triplet near L. We infer, therefore, that this is the order of persistency of these lines under the circumstances. We have before remarked upon the necessity of avoiding all rubber connexions in the construction of pumps employed in the exhaustion of tubes for spectroscopic observation, and we described a modification of the Sprengel pump which we had constructed for this end (' Roy. Soc. Proc., ' vol. 30, p. 499). The warnings of unexpected impurities given by photographs of the ultra-violet spectra of vacuous tube have shown the necessity of preventing the contact of the mercury employed with the dust and moisture of the atmosphere. Hence we have used in the experiments described in this paper a mercurial pump constructed wholly of glass, and in which the same mercury is nsed over and over again without being exposed to any unfiltered air. For this pump we are indebted to the ingenuity and skill in glassblowing of Mr. Lennox of the Royal Institution. The annexed figure (2) represents its construction. A is a reservoir which communicates by the tube aa, which ascends vertically some distance in order to prevent any mercury being driven into the exhausted tube, through the spiral tube ss, with the tube to be exhausted. B is the reservoir of mercury, to the bottom of which the tube gee passes through the sealed joint d. The upper part of B can be put in communication through the three-way cock E, either with the vessel C or with the outer air through the tube D..