﻿948 Mr. J. J. Manley on the 



electrons colliding inelastically must be produced by succes- 

 sive impacts or by absorption of radiation of suitable 

 frequency. The electron normally in the 1*5 S orbit of the 

 sodium atom may be forced into the 2p orbit by direct 

 impact. It is possible, however, that the ejection may be 

 brought about by absorption of radiation of frequency 

 1*5 S — 2p. Before it is .able to return to the 1/5 S orbit and 

 emit this radiation, collision occurs with a second electron, 

 and the electron within the atom is ejected to an orbit still 

 farther removed from the innermost stable orbit It then 

 returns to the 1*5 8 orbit in two stages, the first step causing 

 the emission of a line in the subordinate series, the second 

 step giving the D lines. The chances of this type of 

 collision occurring will increase as the density of the 

 free electrons becomes greater. This also explains why the 

 subordinate series lines are very faint compared with the D 

 lines when an electric discharge is sent through the lamp, 

 for the current density in this case is comparatively small. 



LXXXII. The Protection of Brass Weights. By J. J. 

 Manley, M.A. y Research Fellow, Magdalen College, Oxford*". 



SIXTEEN years ago, I applied to a set of brass weights 

 a method introduced by Faraday for protecting iron 

 from rust ; and as the experiment has been highly successful, 

 other workers may find the plan, or a modification of it 

 described below, helpful. 



The weights, some of them badly corroded, were first 

 lightly tooled and then suitably polished ; next they w r ere 

 heated in a semi-luminous gas flame until they were nearly 

 red hot, and then suddenly plunged into boiled linseed oil, 

 wherein they were left to cool. The weights having been 

 removed from the oil, were washed with turpentine and then 

 polished with old linen; subsequently they were adjusted, 

 standardized, and set apart for the use of students beginning 

 their course of Quantitative Chemistry. Now, although the 

 weights have been in regular use throughout the 16 years 

 that have since elapsed, and have been subjected to what 

 may be rightly termed the severest test of laboratory con- 

 ditions and usage, numerous re-standardizations, the most 

 recent of which was carried out a few weeks ago, have con- 

 clusively shown that Faraday's method for the protection of 

 iron is also remarkably effective when applied to brass, and 



* Communicated bv the Author. 



