MEMOIR. 



xlvii 



that there is a material difference in the 

 manner in which we acquire our ideas of 

 the primary and secondary qualities of 

 matter*. If, after a closer examination 

 of this subject than I had formerly given 

 it, I should have found, that my notions 

 respecting it were just, I should have at- 

 tempted in treating of it, to imitate, in 

 some slight degree, the inimitable manner 

 employed by Berkeley in his Treatise on 

 Vision. I should then have presented to 

 the Royal Society several papers on vision, 

 the chief of which would have treated of 

 those phenomena of light, which have been 

 denominated by authors coloured shadows, 

 ocular spectra, and by various other titles. 

 In the last place, I should have brought 

 together into one volume, all my publica- 



* He made out, in his own hand- writing, during his 

 last illness, a short statement of his opinion upon this 

 subject, which, by his desire, has been put, since his 

 death, into the hands of a philosopher, whose great learn- 

 ing and profound researches into the human mind pecu- 

 liarly fit him for estimating it justly. E. 



