MarcH 29, 1912] 
experienced in finding common ground upon which 
to stand. At the afternoon session of the same 
day the retiring chairman of Section B gave his 
vice-presidential address upon ‘‘The Work of the 
Electrical Division of the Bureau of Standards.’’ 
This is printed in full in the January 5 number 
of Screncre. Then followed an address by Pro- 
fessor H. A. Wilson, on ‘‘The Structure of the 
Atom,’’ and by Director S. W. Stratton, on ‘‘ The 
Work of the Bureau of Standards.’’ 
The following are abstracts of these addresses: 
The Structure of Atoms: Professor H. A. WILSON, 
McGill University. 
The essential constituent of matter appears to 
be electricity; recent researches, experimental and 
theoretical, suggest that electricity is in fact the 
only constituent of matter. 
Free negative electrons can be obtained from 
almost any form of matter by heating, by the 
action of ultra-violet light or in other ways. The 
optical properties of matter are now explained by 
the presence of negative electrons; the Zeeman 
effect and dispersion may be specially mentioned. 
Many of the electrical and thermal properties of 
metals have been satisfactorily explained by sup- 
posing that metals contain negative electrons 
which move about inside them like the molecules 
of a gas. 
Negative electrons must therefore be regarded 
as a universal constituent of all forms of matter. 
These electrons, moreover, are with good reason 
believed to be simply minute particles of negative 
electricity of much less than atomic size. 
Electrically neutral matter must contain as much 
positive electricity as negative; it is clear, there- 
fore, that all matter must also contain positive 
electricity. One of the most important results of 
recent electrical researches is the fact that while 
free negative electrons can be easily obtained from 
any kind of matter, positive electricity is always 
associated with at least one atom and never ap- 
pears in the form of positive electrons. Positively 
charged molecules seem to be in all cases the result 
of the removal of negative electrons from neutral 
molecules. Since it appears that all negative elec- 
tricity is made up of equal particles and since it is 
very probable that any atom can be exactly neutral 
it follows that the amount of positive electricity in 
any atom must be an exact multiple of the charge 
of one negative electron. This makes it probable 
that positive electricity is also made up of equal 
parts, but so far they have not been obtained free. 
The absence of effects due to the earth’s motion 
SCIENCE 
511 
relative to the ether can be explained on the elec- 
tromagnetic theory if it is supposed that this 
theory covers all phenomena. This appears to be 
a strong argument in favor of the purely electrical 
nature of matter. 
It will be convenient now to mention the chief 
electrical theories of atomie structure which have 
been proposed. 
According to Sir J. J. Thomson, atoms consist 
of solid spheres of positive electricity inside which 
negative electrons move about freely. If the 
sphere is taken to be of uniform density then a 
negative electron is attracted towards the center 
with a force proportional to its distance from the 
center. The electrons of course repel each other. 
The electrons will distribute themselves uniformly 
throughout the sphere so as to neutralize it as com- 
pletely as possible and can vibrate about their 
positions of equilibrium. According to Sir J. 
Larmor, atoms consist of a number of positive and 
negative electrons describing orbits about each 
other. There may be rings of electrons revolving 
round concentric rings. On this view an atom 
is a sort of small gaseous nebula without any sort 
of solid foundation. 
A third theory recently adopted by Rutherford 
regards the atom as containing a nucleus of posi- 
tive electricity with negative electrons outside it; 
probably describing orbits around it. On this view 
the atom is a sort of minute solar system. The 
positive nucleus will always require the same num- 
ber of negative electrons to keep it neutral so that 
it provides a definite foundation fixing the identity 
of the atom. The same may be said of the sphere 
in Sir J. J. Thomson’s theory. 
I shall now proceed to very briefly review some 
of the evidence as to the nature of atoms that can 
be derived from different branches of physics and 
to consider how far the theories mentioned are 
consistent with it. 
The most important property of atoms is their 
extraordinary stability in presence of each other. 
For example, the atoms in a compound molecule 
are very intimately associated and yet they pre- 
serve their identity even at the highest tempera- 
tures. The molecules in a gas are continually col- 
liding violently with other molecules, yet the atoms 
are not destroyed. Negative electrons can be 
knocked out of atoms by the impact of rapidly 
moving particles such as the cathode rays and a 
rays, yet the atoms retain their identity and after 
regaining negative electrons are unaffected. Facts 
like these appear to be decisive against Sir J. 
Larmor’s theory. On this theory we should expect 
