180 
NATURE 
[JUNE 22, 1899 
the same as that which produces the corresponding 
series A,, A,, Az, &c.,in cadmium, and the same for the 
corresponding sets in the other metals of this chemical 
group. In other words, we. are led to suspect that, not 
only is the atom a complex composed of an associa- 
tion of different ions, but that the atoms of those 
substances which lie in the same chemical group are 
perhaps built up from the same kind of ions, or at 
least from ions which: possess the same e/7, and that 
the differences which exist in the materials thus con- 
stituted arises more from the manner of association of 
the ions in the atom than from differences in the funda- 
mental character of the ions which build up the atoms ; 
or it may be, indeed, that all ions are fundamentally the 
same, and that differences in the value of e/7z, or in the 
character of the vibrations emitted by them, or in the 
spectral lines produced by them, may really arise from 
the manner in which they are associated together in 
building up the atom. 
This may be an unjustified speculation, but there can 
be no doubt as to the fascination which inquiry of this 
kind has always exerted, and must continue to exert, 
over the human mind. It is the speculation of the 
ignorant as well as of the philosophic and trained 
scientific mind, and even though it should never be 
proved to rest on any substantial basis of fact, it will 
continue to cast its charm over every investigator of 
nature. 
It is ever the desire of the human mind to see all the 
phenomena of nature bound by one connecting chain, 
and the forging of this chain can be realised only 
gradually and after great labour in the laboratories of 
science. From time to time, the hope has been enter- 
tained that metals may be transmuted, and that one 
form may be converted into another ; and although this 
hope has been more generally nurtured by avarice and 
by ignorance rather than by knowledge, yet it is true 
that we never have had any sufficient reason for totally 
abandoning that hope, and even though it may never be 
realised that in practice we shall be able to convert one 
substance into another, even though the philosopher’s 
stone be for ever beyond our grasp, yet when the recent 
developments of science, especially in the region of 
spectrum analysis, are carefully considered, we have, I 
think, reasonable hope that the time is fast approaching 
when intimate relations, if not identities, will be seen to 
exist between forms of matter which have heretofore 
been considered as quite distinct. Important spectro- 
scopic information pointing in this same direction has 
been gleaned through a long series of observations by 
Sir Norman Lockyer on the spectra of the fixed stars, 
and on the different spectra yielded by the same sub- 
stance at different temperatures. These observations 
lend some support to the idea, so long entertained 
merely as a speculation, that all the various kinds of 
matter, all the various so-called chemical elements, may 
be built up in some way of the same fundamental sub- 
stance ; and it is probable that this protyle theory will, 
in one form or another, continue to haunt the domains of 
scientific thought, and remain a useful and important 
factor in our progress, for all time to come. 
Even though it may be that a knowledge of the 
ultimate constitution of matter must for ever remain a 
sealed book to our inquiries, yet, framed as we are, we 
must for ever prosecute the extension of our knowledge 
in every direction ; and in pursuing knowledge it fre- 
quently happens that vast acquisitions are made through 
channels which at first seem most unlikely to lead us 
any further. It has frequently happened that small and 
obscure effects, obtained after much labour and diffi- 
culty, have led to results of the highest importance, 
while very pronounced and striking effects which have 
forced themselves on the attention of the observer have 
NO. 1547, VOL. 60] 
proved comparatively barren. It was by a determined 
effort of this kind, founded on a correct appreciation of 
the importance of small outstanding differences—so 
small as to be despised or passed over by all other 
observers—that Lord Rayleigh discovered a new gas in 
our atmosphere, added argon to our list of elements, and 
initiated the attack which led to the brilliant capture by 
Prof. Ramsay of several new terrestrial substances. 
Viewed from this standpoint, I hope I am to some 
extent justified in occupying your attention this evening 
with the consideration of the action of magnetism on 
light, for although the effect produced is small and not 
easy to observe, yet, it is likely to prove an important 
instrument of research in the study of matter, and it 1s 
not inappropriate that a public account of what has been 
already achieved should be given in this Institution, in 
which the inquiry was first begun by Faraday, and in 
which his spirit still lives. 
THE DOVER MEETING OF THE BRITISH 
ASSOCIATION. 
= meeting of the British Association in Dover on 
September 13 this year promises, on account of its in- 
ternational character, to be a memorable one in the history 
of the Association. Dover was selected, though it is a 
smaller town than is usually chosen for these meetings, 
on account of its nearness to the French coast, in order 
that an interchange of visits should take place between 
the British Association and its French counterpart, which 
meets this year at Boulogne. The French Government 
has taken a great interest in the arrangements for the 
meeting, rightly judging that the meeting cannot but pro- 
mote friendship and good will between the two nations. 
A good illustration of the truth that science has no 
nationality will be found in the fact that one of the 
evening lectures in Dover will be delivered in French by 
Prof. Chas. Richet, of Paris, on “La vibration Ner- 
veuse.” This will take place on Friday, September 15, 
at 8.30 p.m. It is extremely probable that Prof. Fleming 
will find some way of imparting an international character 
to his lecture on the “ Centenary of the Electric Current,” 
to be delivered on Monday, September 18. 
The preliminary arrangements for the meeting are well 
in hand. The usual handbook is being prepared under 
the editorship of Dr. Sebastian Evans, brother of the ex- 
President of the Association, and will deal with Dover 
both in its ancient and modern aspect. The historical 
part of the subject has been undertaken by the Rev. S. 
P. H. Statham, Chaplain to the Forces, who has recently 
written a history of the castle, town, and port of Dover. 
The geology of the district is in the able hands of Prof. 
Boyd Dawkins ; the botany in those of Mr. Sydney 
Webb. Dr. Parsons undertakes the climate, health and 
meteorology of Dover; whilst the harbour and cross- 
Channel traffic is described by Mr. A. T. Walmisley, 
C.E., the Harbour Board Engineer. This portion of the 
handbook should be extremely interesting in view of the 
national harbour which has been undertaken by the 
Government after more than fifty years’ delay, and which 
will turn Dover into one of our most important naval 
ports. 
For a town of its size Dover possesses an unusually 
large number of rooms suitable for public meetings, so 
little difficulty has been experienced in providing for the 
Sections. The Town Hall, with its annexe, the ancient 
Maison Dieu, will serve for the President’s address and 
the soirées. The School of’ Art, in which five of the 
Sections assemble, adjoins and communicates with the 
Town Hall. The reception rooms and offices have an 
ideal Zoca/e in the buildings and grounds of the Dover 
College. This institution was founded some thirty 
