362 



NATURE 



[August i8, 1904 



measure, which, as a recent writer in these columns, 

 in reviewing the collected papers, July 30, 1903, 

 observed, " exhibits in a marked degree Lord Ray- 

 leigh's great capacity for seeing distinctly the essential 

 point of an experiment or a measurement and keeping 

 that clearly in view throughout. This indeed is a 

 distinguishing feature of his experimental work, a 

 main factor in his success. Those who knew 

 the Cavendish Laboratory when the electrical 

 measurements were going on, or have since 

 visited the laboratory at Terling, from which no 

 less important work is continually being published, 

 have sometimes been astonished at the makeshift 

 character of much of the apparatus. Contrivances of 

 wood and wire and wax do duty where most men would 

 use apparatus elaborated with a quite unnecessary 

 care; but in Lord Rayleigh's case, while the essential 

 instrument on which the accuracy of the investigation 

 really depends is as perfect as the skill of the work- 

 man can make it, and in addition has been thought 

 out in all its details so as to fit it best for the purpose 

 immediately in view, for the rest the arrangement 

 which comes first to hand is utilised without regard to 

 appearances." 



The Cambridge period came to an end in 1884, but 

 previously to this, in his address as president of the 

 mathematical and physical section of the British 

 Association in 1882, Lord Rayleigh had indicated what 

 the next series of experiments were to be. He referred 

 on that occasion to the supposed relation between the 

 atomic weights of the chemical elements as a subject 

 inviting investigation, and continued, " The time has 

 perhaps come when a redetermination of the densities 

 of the principal gases may be desirable — an under- 

 taking for which I have made some preparations." 

 Two years later, when president of the association at 

 Montreal, speaking of the value of the study of electro- 

 lysis as affording a deeper insight into the nature of 

 chemical reaction, he remarked, " And if I might 

 without presumption venture a word of recommend- 

 ation it would be in favour of a more minute study of 

 the simpler chemical phenomena." 



From this time forward Lord Rayleigh has devoted 

 much of his time to the work thus indicated, publish- 

 ing papers in 1887 and 1889 respectivelv on the relative 

 densities of hydrogen and oxygen and on the composi- 

 tion of water in which results are given bearing on 

 Front's hypothesis. 



The first article in the fourth volume of the collected 

 papers is a letter to this Journal, which begins : — " I 

 am much puzzled by some recent results as to the 

 density of nitrogen, and shall be much obliged if any 

 of your chemical readers can offer suggestions as to 

 the cause. According to two methods of preparation 

 I obtain quite distinct values. The relative difference, 

 amounting to about i/iooo part, is small in itself " 

 — the difference ultimately found was 1/200 — " but 

 it lies entirely outside the errors of experiment, and can 

 only be attributed to a variation in the character of 

 the gas"; and his paper concludes, "Is it possible 

 NO. 1816, VOL. 70] 



that the difference is independent of impurity, the 

 nitrogen being in a different (dissociated) state? " 

 This, which was published in 1892, was the first in- 

 dication of the discovery of argon. 



In the following year, 1893, Lord Rayleigh com- 

 municated to the Royal Society a paper on the densi- 

 ties of the principal gases, containing absolute deter- 

 minations with all the precautions that recent physical 

 experience or theory could suggest. Here again he 

 points out that nitrogen prepared from ammonia is 

 lighter than atmospheric nitrogen by something of 

 ihe order of one-half per cent. ; he excludes the possi- 

 bility of contamination by any known substance, which 

 suggests, as before, that an explanation is to be looked 

 for in a dissociated state of the nitrogen itself. In April, 

 1894, he returned to the problem by way of further 

 assuring himself by experiments on actual measured 

 contamination of the absence of known impurities, and 

 as against the dissociation hypothesis ascertained that 

 keeping the lighter nitrogen for eight months did not 

 increase its density. Chemical nitrogen was shown to 

 differ from atmospheric nitrogen. As it appeared that 

 the impurity could not be removed by known processes, 

 and could hardly be in the chemical nitrogen, the next 

 step was to remove the nitrogen from the atmospheric 

 gas. This was essayed by Lord Rayleigh by combin- 

 ation of the nitrogen through the agency of the electric 

 discharge, and by Sir William Ramsay, who had 

 become associated in the work, by passing it over 

 heated magnesium. Both workers were able to 

 announce to the British Association at Oxford the dis- 

 covery of a residue constituting a new gaseous con- 

 stituent of atmospheric air. Then followed the joint 

 memoir of Rayleigh and Ramsay on the isolation and 

 properties of argon. 



This physico-chemical work has been since con- 

 tinued in various forms, the physical properties of 

 argon and of other gases have been investigated, and 

 in particular attention has been given to the accuracy 

 with which Boyle's law is satisfied at the ordinary 

 temperature. This investigation has been extended 

 from pressures of o-oi mm. of mercury up to 150 mm., 

 and the research is still in progress. 



In addition to this physical work, numerous mathe- 

 matical papers, chiefly on problems relating to wave 

 motion and vibrations, should be mentioned. 



Meanwhile, wide as has been the field of pure science 

 covered by Lord Rayleigh's activities, he has found 

 time to spare for the promotion of the application of 

 science to industry and commerce. He was a 

 prominent member of the Board of Trade Committee 

 on Electrical Standards, to which we owe the legal 

 definitions of the ohm, the ampere, and the volt. He 

 presided over the Treasury Committee which recom- 

 mended the establishment of the National Physical 

 Laboratory, and for the past five years has been chair- 

 man of the executive committee of the laboratory. To 

 his wise counsels and guidance much of its success 

 is due. Recently he has been a member of a Board 

 of Trade Committee on methods of testing gas, while 



