14 THE PRESIDENTIAL ADDRESS. 
I have chosen the preceding subject for this address, partly because it 
has not recently been reviewed at these meetings, and also for the opportu- 
nity it has given of urging one or two special points. It is evidently far 
from exhausted—the loose ends have indeed been manifest—but this should 
render it more interesting. It furnishes also an instance, not so familiar 
as some, of the way in which speculations which appear remote from 
common interests may ultimately have an important influence on the pro- 
gress of science. Itis true that the secular investigations into the form of 
the earth’s surface have an importance in relation to Geodesy, but certainly 
no one at the time of Laplace’s work on this matter would have guessed 
that he was unwittingly laying the foundation of the whole mathematical 
theory of electricity. The history of science is indeed full of examples where 
one branch of science has profited by another in unexpected ways. I would 
take leave just to mention two, which happen to have specially interested 
me. It is, I think, not generally understood what an important part the 
theory of elasticity played in Rayleigh’s classical determinations of the 
relative weights of the gases, where it supplied an important and indeed 
essential correction. Again, the mathematical theory of Hydrodynamics, 
in spite of some notable successes, has often been classed as a piece of 
Pure Mathematics dealing with an ideal and impossible fluid, elegant 
indeed, but helpless to account for such an everyday matter as the turbulent 
flow of water through a pipe. Recently, however, at the hands of Prandtl, 
it has yielded the best available scheme of the forces on an aeroplane, and 
is even being appealed to to explain the still perplexing problem of the 
screw-propeller. 
To promote this interaction between different branches of science is one 
of the most important functions of our Association, and differentiates it 
from the various sectional congresses which have from time to time been 
arranged. We may hope that this meeting, equally with former ones, may 
contribute to this desirable end. 
Let me close with a local reference. The last fifty years have seen the 
institution of local universities and university colleges in many parts of 
this country and of the Empire at large. Through these agencies the 
delights of literature, the discipline of science, have been brought within 
the reach of thousands whose horizons have been enlarged and their whole 
outlook on life transformed. They have become centres, too, from which 
valuable original work in scholarship, history, and science, has radiated. 
The University College of Southampton is now contemplating an increased 
activity and a fuller development. In this ambition it has, I am sure, the 
best wishes of us all. 
