President's Address. 
59 
We owe it, not to the telescope of the astronomer, but to the pen of 
the mathematician. And surely it would be hard to find in the history 
of the human intellect anything more irresistibly attractive to the 
imagination — more poetic (if I may use the word) — than the thought 
that on that scribbled page, in those grotesque symbols, lay a power 
which enabled the mathematician to look up from his table in the 
solitude of his own study — to point to the heavens with the unerring 
finger of Science, and to say — I cannot see it, but it is there. 
I have already, in treating of Applied Mathematics, spoken at some 
length, incidentally, of that branch of Science, which we commonly 
call Experimental Physics, and which I might indicate geographically 
by saying, that it is bounded by Applied Mathematics on the one side, 
and by Chemistry on the other. But neither of the boundaries is 
a very sharp one ; and of the second, more especially, I may say, that 
the constant tendency of Science is to obliterate it. There are, indeed 
(to continue the geographical form of expression), large tracts of either 
territory in which the right of property is clear enough. Eut there is 
also on the frontier a great and increasing region, where the two dis- 
tricts overlap — to which neither has an exclusive title, but which 
may truly be said to belong to both. And the history of modern 
Science shows every day more clearly that this border land" is pecu- 
liarly fruitful in discovery. This alone would sufficiently justify the 
mode in which I wish to treat this part of my subject. But there is 
another reason, which even more concerns my present audience — 
namely, that this region may be most advantageously worked by a 
mixed society like ours. I am very far indeed from undervaluing 
societies specially devoted to the study of Chemistry. They have 
their function to discharge ; and an important function it is. But 
I think we may say, that their proper sphere is to be found, rather in 
those problems which can be solved by the powers of Chemistry alone, 
than in those which will yield only to an alliance of Chemistry with 
some other science. IN'ow such an alliance may fitly find a place in 
the Royal Irish Academy. We who are limited to no one science — who 
number among our members labourers in every part of the scientific field, 
may profitably attempt the solution of problems requiring the force of 
more than a single science, and therefore not coming so properly within 
the scope of a society whose field of labour is more limited. 
Applying this principle to our present subject, I would indicate, as 
an alliance which has already been very fertile — an alliance whose 
powers, far from being exhausted, are but now beginning to make 
themselves known — the combination of Optics and Chemistry. What 
it has effected already — how the science of Optics has reacted upon 
Chemistry, endowing it with an analysis, refined and powerful beyond 
any which it has hitherto possessed — giving it to know of new ele- 
ments which, unaided, it might never have discovered — how both these 
sciences combined have reacted upon Astronomy, placing, we may truly 
say, the immeasurably distant star in the laboratory of the chemist, 
and enabling him to detect in its atmosphere the presence of nitrogen 
