1845] WRITINGS OF JOSEPH HENRY. 237 



phers gave it the name of Daltonism. To this name however 

 several British writers have strongly objected. If this sys- 

 tem of names were once allowed, say they, there is no telling 

 where it would stop : the names of celebrated men would be 

 connected, not with their superior gifts or achievements, but 

 with the personal defects which distinguish them from their 

 more favored but less meritorious contemporaries. Professor 

 Whewell proposed the term Idiopts, signifying peculiarity 

 of vision ; but to this name Sir David Brewster properly ob- 

 jected, that the important consonant p would be very apt to 

 be omitted in ordinary pronunciation, and so the last state 

 of the Idiopt would be worse than the first. The name color- 

 blindiiess, suggested by Sir David, although not in all cases 

 free from objection, is perhaps better than any we have seen 

 proposed. 



It has already been stated that the number of persons 

 affected with color-blindness is much more considerable than 

 is generally imagined. They are often themselves ignorant 

 of their imperfection of vision, particularly when it is 

 restricted to the want of power to discriminate between colors 

 nearly related to each other. Professor Seebeck found five 

 cases among the forty boys who composed the two upper 

 classes of a gymnasium of Berlin. Professor Prevost, of 

 Geneva, stated that they amounted to one in twenty ; and 

 Professor Wartmann does not think this estimate much ex- 

 aggerated 



Observations on this peculiarity of vision have as yet been 

 confined, so far as we know, to Europe, with the exception 

 of two cases described b}' Dr. Hays, of Philadelphia, in the 

 Proceedings of the American Philosophical Society. It has 

 also as yet been found only among the white race, although 

 sufficient observations have not been made to render it prob- 

 able that it is confined to this variety of the human family. 

 The question has been asked, whether there is any external 

 sign by which to detect, with simple inspection of the visual 

 organ, a case of color-blindness. Professor Wartmann re- 

 marks, that he would not venture to give an answer to this 

 question in all cases in the negative. I have observed, says 



