PRESIDENTIAL ADDRESS. 481 



PasteUf, of Maxwell, of Lister, and of Kelvin, the change in the public altitude 

 would bo real, evident, and fruitful. 



lu conclusion, one is tempted to seek for the underlying cause of the accelera- 

 tion in the rate of advance of natural knowledge. Is it to be found in the 

 increase in power of the human intellect, or the diversion into one particular 

 channel of activities previously otherwise employed? It is possible that the 

 human intellect has, by the processes of evolution, become more powerful, and that 

 man's ability to decipher the secrets of Nature has thereby increased. I think, 

 however, that it would require a bold advocate to support this thesis. If any such 

 mental evolution has taken place, it is strange that it should be restricted to one 

 particular sphere of activity. Are our poets and authors of to-day greater than 

 Homer, our statesmen than Pericles ? Or, passing into the domain of science, can 

 we say with confidence that, in pure power of reasoning. Maxwell was undoubtedly 

 the superior of Archimedes ? 



I have elsewhere indicated what appears to me to explain the mystery of this 

 acceleration, namely, the extension of our senses by mechanical appliances. When 

 we supplement our eyes 'by the bolometer and the electric coherer, the range of 

 our vision is augmented a thousandfold. By the use of the electroscope and the 

 galvanometer we have extended our senses of sight and touch until we can detect 

 the presence of an electron. 



Having realised the imperfection of our faculties, we have called upon Nature 

 in all departments of science to supply our deficiencies, and are thus enabled to 

 walk with confidence where previously all seemed dark. 



From the time of Archimedes to that of Bacon we despised Natural Knowledge, 

 while we deified intellect and authority ; hence for nearly two thousand years our 

 record was one of retreat rather than advance. When the philosopher left his study 

 and applied his powers of observation to the phenomena of the universe, progress 

 became a reality, and thenceforward the march of discovery has known no backward 

 step. We have therefore every reason to believe that when the Association again 

 visits this ancient city our President will be able to chronicle an increase in Natural 

 Knowledge even greater than that which has been one of the distinguishing 

 characteristics of the last quarter of a century. 



The following Papers were read :— 



1. Photogra/phs of the Arc Spectrum of Iron under High Presstires. 



By W. G. DUFFIELD. 



Using a pressure-cylinder designed by Dr. Petavel, photographs of the arc 

 spectrum of iron have been taken in air at pressures ranging from 1 to 100 atmos- 

 pheres. Slides showing the displacement of the lines from their normal positions 

 under high pressures were shown to the Section, and attention was drawn to the 

 behaviour of reversed lines. Under a pressure of 100 atmospheres displacements 

 amounting to one Angstrom unit had been measured. 



2. Meastirements of Osmotic Pressure. By the Earl of Berkeley, F.G.S. 



FRiDAYi AUGUST Z. 



Discussion on the Evolution of the Elements. 

 Opened by F. Soddy. — See Reports, p. 121. 



1906. 



II 



