A76 TRANSACTIONS OF SECTION B. 
than that of the physicist. Spectrum analysis arose under the joint influence of 
Bunsen and Kirchhoff, and I think its problems still call for more combined work 
on the part of chemist and physicist than has latterly been the custom. 
Having given a short summary of the present state of knowledge on one par- 
ticular chemical topic, I may perhaps be permitted to conclude my Address with 
a few general observations relating to the science as a whole. 
The contemplation of such a life as that of Berthelot makes us realise in a 
vivid way the progress of chemical science. He was a chemist without limitation, 
his activity extending over the whole range of the science, physical, inorganic, and 
organic. Whilst we must not forget his exceptional powers, we cannot help 
feeling how different in its extent was our science when he entered upon his 
labours from what it was when they ceased, and we cannot help feeling how vain 
it now is for anyone to hope for so imperial a sway. 
Yet it is difficult to believe that the state of chemistry can ever have been 
more interesting than it is at the present moment, or that anyone who sighs for 
the good old times can do so from anything but the love of a quieter life. We 
need not go back more than twenty years to find a sharp contrast. At that time 
there was indeed no want of activity, but it was that of a band of travellers who 
had left their frontier adventures far behind, and were marching steadily over a 
wide and almost uninterrupted plain. To-day we are among the mountains, 
with new peaks and prospects appearing on every side. Truly a steady head is 
required ; and well may we ask, Whither are we going and where is the path of 
progress and of safety? I rejoice to live in such times; but J feel no competence 
to describe them, still less can I pretend to have vision keen and comprehensive 
enough to let me figure as a guide. 
One of the penalties of devotion to a progressive science is the constant feeling 
of being left behind, and the knowledge that, while we are attending to our 
personal task, things are happening, near or far, that may, for all we know, be 
affecting the simplest facts andthe most elementary principles on which we have 
been accustomed to rely. This is a feeling that may well prevail at the present 
day. At the same time I do not think there is any occasion for panic, 
and I cannot help regretting the somewhat sensational language that has been 
used, even within our own circles, in regard to recent discoveries. The 
revelations attendant upon the investigation of radio-activity do indeed mark 
a distinct epoch in the history of chemical discovery, but that they entail 
anything like an unsettlement of our scientific articles of faith is not to 
be admitted for a moment. They make us realise in perhaps a not unprofit- 
able way that scientific knowledge and scientific theories are necessarily proximate, 
never ultimate, and that ideas which may have been entertained for a long time 
without modification, and so have begun to seem perpetual, are, after all, only 
provisional, 
There is certainly some embarrassment on finding that a substance like radium, 
which according to the conventions would be called a chemical element, breaks up so 
as to give substances which, according to the same conventions, are likewise called 
elements. But the con‘usion is one of terminology and not of ideas. I think it 
likely that few chemists of my own generation have been in the habit of regard- 
ing the conventional elements as the ultimate compositional units of matter. We 
know that in our own country distingnished men of science like Sir William 
Crookes and Sir Norman Lockyer have always insisted on the complex nature of 
the elements, and I suspect there are many among us who might own to having 
made sober, if unsuccessful, attempts at the resolution of elements before the days 
of radium. 
The perplexities of chemists at the present day do not come, I think, from 
the novelty of the ideas that are being presented to them, but from the great 
rapidity with which the whole science is growing, from the invasion of chemistry 
by mathematics and, in particular, from the sudden appearance of the subject 
of radio-activity with its new methods, new instruments, and especially with 
its accompaniment of speculative philosophy. There is an uneasy feeling that 
