PRESIDENT’S ADDRESS. 13 
The small number of degrees of freedom of a molecule, and the 
subdivision of its total energy into equal parts corresponding thereto, 
is a theme not indeed without difficulty but full of importance. It is 
responsible for the suggestion that energy too may be atomic! 
Mendelejefi’s series again, or the detection of a natural grouping of 
atomic weights in families of seven, is another example of the signi- 
ficance of number. 
Electricity was found by Faraday to be numerically connected with 
quantity of matter; and the atom of electricity began its hesitating but 
now brilliant career. 
Electricity itselfi—i.e. electric charge—strangely enough has proved 
itself to be atomic. There is a natural unit of electric charge, as 
suspected by Faraday and Maxwell and named by Johnstone Stoney. 
Some of the electron’s visible effects were studied by Crookes in a 
vacuum; and its weighing and measuring by J. J. Thomson were 
announced to the British Association meeting at Dover in 1899—a 
fitting prelude to the twentieth century. 
An electron is the natural unit of negative electricity, and it may not 
be long before the natural unit of positive electricity is found too. But 
concerning the nature of the positive unit there is at present some divi- 
sion into opposite camps. One school prefers to regard the unit of 
positive electricity as a homogeneous sphere, the size of an atom, in 
which electrons revolve in simple harmonic orbits and constitute nearly 
the whole effective mass. Another school, while appreciative of the 
simplicity and ingenuity and beauty of the details of this conception, and 
the skill with which it has been worked out, yet thinks the evidence 
more in favour of a minute central positive nucleus, or nucleus-group, 
of practically atomic mass; with electrons, larger—i.e. less concen- 
trated—and therefore less massive than itself, revolving round it in 
astronomical orbits. While from yet another point of view it is in- 
sisted that positive and negative electrons can only differ skew-symmet- 
rically, one being like the image of the other in a mirror, and that the 
mode in which they are grouped to form an atom remains for future 
discovery. But no one doubts that electricity is ultimately atomic. 
Even magnetism has been suspected of being atomic, and _ its 
hypothetical unit has been named in advance the magneton: but I con- 
fess that here I have not been shaken out of the conservative view. 
We may express all this as an invasion of number into unsuspected 
regions. 
Biology may be said to be becoming atomic. It has long had 
natural units in the shape of cells and nuclei, and some discontinuity 
represented by body-boundaries and cell-walls; but now, in its laws of 
heredity as studied by Mendel, number and discontinuity are strikingly 
apparent among the reproductive cells, and the varieties of offspring 
