146 ANNUAL OF SCIENTIFIC DISCOVERY. 



power?, and learn whether they refer to an optical appreciation of the chemi- 

 or heal rays, or show any modification of the solar spectrum by enlarge- 

 ment or otherwise. 



Lastly, it would be well, when children show an unusual difficulty in de- 

 scribing colors, to try, by some such experiments as those here related, whether 

 any detect of color-blindness exists or not. It would clearly be undesirable 

 that such children as have this detect should waste time in learning accom- 

 plishments or professions which they must always be unable to practise. They, 

 their parents, and teachers may thus be saved some of that disappointment 

 which is always experienced when presumed tastes and talents are cultivated 

 or forced contrary to the natural powers of the individual. It must clearly be 

 hopeless to endeavor to obtain good taste in colors, when most of the colors 

 themselves are not seen at all, or are so recognized as to present appearances 

 altogether different from those seen by the rest of the world. 



THE CHAMELEON'S CHANGE OF COLOR. 



In IS\H, the celebrated Dutch anatomist,' Vrolik, ascertained the fact of the 

 influence exercised by light on the color of these animals ; and he observed 

 also that there was a constant succession, or oscillation, of colors. Four 

 years later, his countryman, Tan der Hooven, executed the plan of repro- 

 ducing in five different plates the changes of color he observed. These show 

 that the fundamental color of the animal persists under all the variations 

 which may take place in parts. He observes that the median line, from the 

 chin downwards, is always of one yellow tint. In his opinion the changes of 

 color are due to a pigment underneath the skin. This idea was taken up by 

 Milne-Edwards, who had two chameleons with different shades of color: the 

 one presenting violet-spots on its flanks ; the other, green spots of varying 

 shade. He observed that the change of color was quite independent of the 

 animal's swelling himself out or not. On removing a strip of skin from the 

 dead animal, and placing it under a microscope, he observed that the darkest 

 color was beneath the tubercles, and that in these spots the yellow color was 

 masked, but not replaced; it still existed, although the violet spots beneath 

 it rendered it invisible. Two pigments therefore are possessed by the 

 chameleon: one, the yellow pigment, being distributed over the surface; 

 the other, the violet pigment, being distributed underneath tie former, and 

 only becoming visible under certain circumstances, such as the stimulus 

 of light. Milne-Edwards found that, on stimulating the yellow spots with 

 alcohol or acids, they became violet ; on stimulating the violet spots they 

 became yellow. 



And thus, after many centuries of easy fable and reiterated assumptions, 

 the more arduous but more fruitful methods of exact science gained the key 

 to the whole mystery. But only the key. Milne-Edwards had explained the 

 and black hues, but had not explained the others. That was reserved 

 for Prof. Bruecke, of Vienna. He has succeeded to the satisfaction of men of 

 cience; but as it would require more technical knowledge to understand his 

 explanation than can be expected of the ordinary reader, and would lead ns 

 _:h beyond our limits, we will merely add", that his observations show 

 the chameleon has his own colors, and does not borrow them from sur- 

 rounding objects ; if he sometimes shows more of one than of another, it is 

 that, like a ne-ro maiden blushing, the emotions of his soul are eloquent 

 on his surface, but simply that the rays of li-ht act upon his skin. After 



