1885.] Prof. K. Pearson, On a certain atomic hypoti hesis. 223 



(2) On a certain atomic hypothesis. By Prof. K. Pearson, 

 communicated by H. T. Stearn, M.A. 



[Abstract] 



The paper deals with the motion of a number of spherical 

 portions differentiated off from a continuous medium and pulsating 

 uniformly over their surfaces. Each of these spheres, called in 

 the paper an atom, has a natural period of free pulsation, depending 

 on its mass and the potential energy it is supposed to possess. 

 This natural period is modified by the presence of other atoms of 

 the same or different period, and a form of expression is found 

 for the resulting period of a system of a number of atoms exerting 

 mutual influence on each other. Such a system is called a mole- 

 cule ; the atoms of one molecule are supposed not to affect the 

 period of vibration of another molecule, the average distance 

 between two molecules being great compared with that between 

 two atoms. 



Expressions are found for the forces arising from the motion : 



(a) between two atoms in the same molecule, called chemical 

 forces ; 



(/3) between two molecules, containing the same or different 

 atoms, in proximity to each other — molecular forces ; 



(7) between groups of molecules at some distances apart. 



The results of the mathematical investigation are applied to 

 some of the phenomena of spectrum analysis, e.g. the relation 

 between the spectra of some of the metalloids and their atomic 

 weights, the effect of pressure in modifying the spectrum of a gas, 

 and the relation between the spectrum of a compound and those 

 of its constituents. 



The paper is being published in full in the Transactions of 

 the Society. 



(3) On a Youngs Eriometer. By R. T. Glazebrook, M.A., 

 F.R.S. 



The author exhibited and described an " eriometer," an in- 

 strument for measuring the diameter of fine fibres, and so testing 

 the value of different qualities of wool, which belonged to Thomas 

 Young, and on which there was a description in his handwriting. 



1G— 2 



