1907.| Anniversary Address by Lord Rayleigh. 77 
with the subject at all, The natural development of Hamilton’s ideas will 
be found in an able memoir by Schwarzschild (1905). 
I have spoken of English work that lay neglected, but a scarcely less 
notable instance is the splendid discovery of the microscopic limit by 
Fraunhofer, a man who combined in the highest degree practical skill with 
scientific insight. Thanks to the researches of Abbe and Helmholtz, it is 
now well known that there is a world that lies for ever hidden from our 
vision, however optically aided ; but neither of these eminent men realised 
that the discovery had been anticipated by’ Fraunhofer. Some, perhaps, may 
doubt whether Fraunhofer’s argument, founded upon the disappearance of 
spectra from gratings of extreme fineness, is of adequate cogency. To this 
I may reply that I was myself convinced by it in 1870, before either 
Abbe or Helmholtz had written a word upon the subject. 
Enough has probably been said to illustrate my contention that much loss 
has ensued from ignorance and neglect of work already done. But is there 
any remedy? I think there ought to be. In all the principal countries of 
the world we have now a body of men professionally connected with science 
in its various departments. No doubt the attention of many of these is so 
engrossed by teaching that it would be hard to expect much more from 
them, though we must remember that teaching itself takes on a new life 
when touched with the spirit of original enquiry. But in the older 
Universities, at any rate, the advancement of science is one of the first 
duties of Professors. Actual additions to knowledge occupy here the first 
place. But there must be many who, from advancing years or for other 
reasons, find themselves unable to do much more work of this kind. 
It is these I would exhort that they may fulfil their function in another 
way. If each man would mark out for himself a field—it need not be 
more than a small one—and make it his business to be thoroughly con- 
versant with all things new and old that fall within it, the danger of which 
I have spoken would be largely obviated. A short paper, a letter to a 
scientific newspaper, or even conversation with friends and pupils, would 
rescue from oblivion writings that had been temporarily overlooked, thereby 
advancing knowledge generally and sometimes saving from discouragement 
an unknown worker capable of further achievements. Another service such 
_ experts might render would be to furnish advice to younger men desirous of 
pursuing their special subject. 
The readers of whom I have been speaking are experts capable of 
advancing science themselves and of helping others to do so. But there is 
another class of possible readers of scientific books on behalf of whom 
I wish to make an appeal. We who are dependent upon sight in almost 
