Conihhiaiion 



SCIENTIFIC SIDE-LIGHTS 



110 



the waters of the seas and oceans, and are 

 thus coextensive with the domain of life 

 upon the earth. WALLACE Darwinism, ch. 

 8, p. 155. (Hum., 1889.) 



542. COLOR-BLINDNESS More Com- 

 mon among Men than among Women De- 

 fect Commonly Congenital. Color-blindness 

 is found much more common among men 

 than women. Out of one hundred and fifty 

 registered cases, there are but six of fe- 

 males, and one of these is doubtful. It has 

 been conjectured that needlework on a va- 

 riety of colored articles might be the means 

 of counteracting the tendency to this defect, 

 as well as to produce a delicacy of discrim- 

 ination of different shades of color not pos- 

 sessed by those otherwise employed. But in 

 answer to this it has been remarked, that in 

 the case of " Daltonians " engaged in paint- 

 ing there has been found but little, if any, 

 improvement of the condition of vision ; and 

 the very employment of the females on 

 works which require a constant comparison 

 of color would daily reveal cases of blind- 

 ness of this kind did it frequently exist in 

 the female sex. This peculiarity of vision is 

 principally congenital. Professor Wartmann 

 has found but two exceptions. In one of 

 these, colors were perceived in the usual 

 manner until at the ninth year, when the 

 boy received a violent blow on the head, 

 which fractured the skull, and rendered a 

 surgical operation necessary. The fact, how- 

 ever, that three of the brothers of this indi- 

 vidual were affected with the same kind of 

 vision renders it probable that he was con- 

 stitutionally predisposed to this peculiarity. 

 HENRY Scientific Works, vol. i, p. 238. 

 (Sm. Inst., 1886.) 



543. COLORS IN DEEP-SEA FISH 



Dark or Dull Hues Prevail. The majority 

 of the fish are dark brown or black, but 

 many other colors are represented. . . . 

 Many examples could be given to show the 

 prevalence in these regions of these black, 

 dull, and pale uniform colors. But there 

 are many exceptional cases. HICKSON 

 Fauna of the Deep Sea, ch. 4, p. 59. (A., 

 1894.) 



544. COLORS OBTAINED FROM THIN 

 FILMS Due to Interference of Light-waves. 

 He [Robert Hooke] then describes fully and 

 clearly the experiment with pressed glasses: 

 " Take two small pieces of ground and pol- 

 ished looking-glass plate, each about the big- 

 ness of a shilling; take these two dry, and 

 with your forefingers and thumbs press them 

 very hard and close together, and you shall 

 find that when they approach each other 

 very near there will appear several irises or 

 colored lines, . . . and you may very 

 easily change any of the colors of any part 

 of the interposed body by pressing the plates 

 closer and harder together, or leaving them 

 more lax that is, a part which appeared 

 colored with a red may be presently tinged 

 with a yellow, blue, green, purple, or the 



like. Any substance," he says, " provided it 

 be thin and transparent, will show these 

 colors." Like Boyle, he obtained them with 

 glass films ; he also " produced them with 

 bubbles of pitch, rosin, colophony, turpen- 

 tine, solutions of several gums, as gum ara- 

 bic in water, any glutinous liquor, as wort, 

 wine, spirit of wine, oil of turpentine, glare 

 of snails, etc." [See COLORS OF THIN 

 PLATES, 548-9.] TYNDALL Lectures on 

 Light, lect. 2, p. 70. (A., 1898.) 



545. COLORS OF SPECTRUM Aris- 

 totle's Theory of Combination of Black and 

 White Experiment Disposes of Ancient Er- 

 ror. Aristotle taught that black and white 

 are the two fundamental qualities of light, 

 and that every color can be obtained from 

 their intermixture in varying amounts. 

 . . . The Aristotelian view of the origin 

 of color prevailed until modern times. 

 Goethe defended it, and many of his admir- 

 ers are its enthusiastic champions. But it 

 has been banished from science these two 

 hundred years, thanks to Newton's discov- 

 eries. Newton said to himself: If there 

 really are simple kinds of light or simple 

 colors, which intermix in various ways, we 

 must be able both to isolate and to recom- 

 bine the simple constituents of any given 

 compound color. That meant that the whole 

 question was referred to the tribunal of ex- 

 periment, where alone it could be definitely 

 answered. For direct perception is decep- 

 tive. Can the chemist " see " of what ele- 

 ments a body is composed? Of course not. 

 We know that bodies of very different 

 chemical composition appear just alike. 

 May not the same hold of light? May not 

 similar kinds of light give rise to different 

 mixtures, and different kinds to similar 

 mixtures? So Newton looked round him 

 for a means of analyzing compound light, 

 and by a happy accident found what he 

 wanted in the refraction of light by the 

 prism. WUNDT Psychology, lect. 6, p. 88. 

 (Son. & Co., 1896.) 



546. COLORS OF STARS Change of 

 Color of Sirius. The Greek astronomers 

 were acquainted with red stars only, while 

 modern science has discovered, by the aid of 

 the telescope, in the radiant fields of the 

 starry heaven, as in the blossoms of the 

 phanerogamia, and in the metallic oxids, al- 

 most all the gradations of the prismatic 

 spectrum between the extremes of refrangi- 

 bility of the red and the violet ray. Ptole- 

 my enumerates in his catalog of the fixed 

 stars six (viroKippot) fiery red stars viz., 

 Arcturus, Aldebaran, Pollux, Antares, a 

 Orionis (in the right shoulder), and Sirius. 

 Cleomedes even compares Antares in Scorpio 

 with the fiery red Mars, which is called both 

 rvpp6 and irvpoeiSfi^. Of the six above- 

 named stars, five still retain a red or red- 

 dish light. Pollux is still indicated as a 

 reddish but Castor as a greenish star. 

 Sirius therefore affords the only example of 



