APRIL 4, 1921 proceedings: philosophical society 1(37 



epoch-making work on mass spectra proving atomic masses of all the elements 

 to be whole numbers excepting hydrogen. Neon, chlorine, argon and many 

 other elements are mixtures of isotopes of different masses but of the same 

 atomic number (the number of positive charges on the nucleus which de- 

 termines its atomic properties). 



Sir Ernest Rutherford followed with a short description of his work on the 

 disintegration of nitrogen and other gases into hydrogen particles moving 

 ■with, greater velocity than the bombarding a-particles themselves. Thus 

 without doubt the hydrogen nucleus is the positive electron and stable groups 

 of minute hydrogen particles, bound together by the much larger negative 

 electrons, such as the helium nucleus (a-particle) form the nuclei of all the 

 heavier atoms. 



Especially interesting also were the remarkable discussion on the Origin of 

 Spectra led by Nicholson, the note of Sir Oliver Lodge on Relativity and the 

 reply of Pres. EddingTon, the evening discourse of Sir Richard Glazebrook 

 on Aircraft and the vote of thanks moved by Dr. StraTTon of our Bureau of 

 Standards. The wealth of things of interest in other branches of science, 

 and the pleasant excursions of all sorts filled every moment of a busy and 

 delightful week. 



Discussion: The paper was discussed by Messrs. Silsbee and SosmaN. 



840th meeting 



The 840th meeting was held at the Cosmos Club, November 6, 1920, with 

 President Sosman in the chair and 32 persons present. The following pro- 

 gram was given : 



E. F. Mueller and T. S. Sligh, Jr.: The hypsonieter as a precision in- 

 strument (presented by Mr. Mueller). 



A very simple form of hypsometer, consisting of a nearly closed space into 

 which steam from a boiler can be admitted, will serve to maintain a tempera- 

 ture in the steam space which differs at most by a very few hundredths of a 

 degree from that corresponding to saturated steam at the prevailing atmos- 

 pheric pressure. The well-known Rudberg or Regnault hypsometer is a 

 Y&ry simple apparatus, and is capable of serving the requirements of all but 

 the most precise thermometric measurements. In the more elaborate de- 

 signs which have been developed at the International Bureau and at the 

 Reichsanstalt, the design has been largely influenced by such considerations 

 as the desirability of being able to read mercurial thermometers in either a 

 horizontal or a vertical position, of measuring accurately the difference be- 

 tween the pressure of the steam and atmospheric pressure, or of avoiding 

 superheating of the steam, the last named feature being particularly empha- 

 sized. Apparently the question of purity of material, or the possibility of 

 the steam being mixed with air, has received only incidental consideration. 



In the design of a new portable hypsometer, advantage was taken of the 

 difference in density of steam and air to insure rapid removal of air from the 

 steam space by introducing the steam into this space at the top. This has 

 the further advantage of rendering the temperature stable with no appreciable 

 excess pressure in the steam space thus dispensing with the water manometer. 

 Electric heating is used and the volume of the boiler is small, so that heating 

 up is rapid. Two sheath heating coils are used which, connected in parallel, 

 provide rapid heating, and connected in series suffice for regular operation. 



Experiments with heat inputs from 125 to 640 watts indicate that such 



