PEESIDENTIAL ADDEESS. 



OOLOUR-SIGET AND COLOUR-BLINDNESS. 



(Plates I. and II.) 



By JOHN THOMSON, M.B. 



( Read before the Royal Society of Queensland, 19th September, 1903) 



On two occasions, in 1900 and again in 1902, the Royal 

 Society of Queensland did me the distinguished honour of 

 appointing me its president — an honour, I need hardly tell you, 

 I very much value. 



To the honour, however, is attached the responsibility — not 

 the pleasing duty of piloting the Society during the year of 

 ■office, for that, thanks to the energies of the Treasurer and the 

 Secretary and the able assistance of the Council, is a labour of 

 love — but the task — the responsibility — of the Presidential 

 Address. 



I take it that the functions of a Royal Society are to 

 encourage original work in every department of physical science, 

 and the purely physical need not be the boundary line, ex- 

 plorations should be conducted even into the uncanny. 



I also take it that the chair of the president permits him to 

 ■engage in the popular, and in acknowledgement of my indebted- 

 ness to the Society for its courtesy to me and in fulfilment of 

 my obligation I have selected for my address to-night the some- 

 what popular, yet I trust interesting, subject, 



"COLOUR-SIGHT AND COLOUR-BLINDNESS." 

 To discuss this, I must lead up to it by endeavouring to 



•explain briefly some of the physical properties of light and the 



physiological conditions of vision. 



