491 



SCIENTIFIC SIDE-LIGHTS 



Newton's Rings Illustrate Interference 

 of Light-waves. Newton . . . determined 

 by accurate measurements the relation of 

 the thickness of the film to the color of dis- 

 plays. [See COLORS OF THIN PLATES; 

 PLATES.] In doing this his first care was 

 to obtain a film of variable and calculable 

 depth. On a plano-convex glass lens . . . 

 of very feeble curvature he laid a plate of 

 glass . . . with a plane surface, thus 

 obtaining a film of air of gradually increas- 

 ing depth from the point of contact ... . 

 outwards. On looking at the film in mono- 

 chromatic light he saw, with the delight 

 attendant on fulfilled prevision, surrounding 

 the place of contact a series of bright rings 

 separated from each other by dark ones 

 and becoming more closely packed together 

 as the distance from the point of contact 

 augmented. . . . When he employed red 

 light, his rings had certain diameters; when 

 he employed blue light, the diameters were 

 less. In general terms, the more refrangible 

 the light the smaller were the rings. Caus- 

 ing his glasses to pass through the spectrum 

 from red to blue, the rings gradually con- 

 tracted; when the passage was from blue 

 to red, the rings expanded. This is a beauti- 

 ful experiment, and appears to have given 

 Newton the most lively satisfaction. When 

 white light fell upon the glasses, inasmuch 

 as the colors were not superposed, a series 

 of iris-colored circles was obtained. . . . 

 In monochromatic light the rings run closer 

 and closer together as they recede from the 

 center. This is due to the fact that at a 

 distance the film of air thickens more rapid- 

 ly than near the center. When white light 

 is employed this closing up of the rings 

 causes the various colors to be superposed, 

 so that after a certain thickness they are 

 blended together to white light, the rings 

 then ceasing altogether. TYNDALL Lectures 

 on Light, lect. 2, p. 72. (A., 1898.) 



2416. NICHE OF SCIENCE UN- 

 FILLED Why Not a Shrine of Deity (Ps. 

 xc, 2)." Does the vital," he [Professor 

 Knight] asks, " proceed by a still remoter 

 development from the non-vital? Or was it 

 created by a fiat of volition ? Or " and here 

 he emphasizes his question " has it always 

 existed in some form or other as an eter- 

 nal constituent of the universe f I do not 

 see," he replies, " how we can escape from 

 the last alternative." With the whole force 

 of my conviction I say, Nor do I, tho our 

 modes of regarding the " eternal constitu- 

 ent " may not be the same. TYNDALL Frag- 

 ments of Science, vol. ii, ch. 15, p. 376. (A., 

 1900.) 



2417. NIGHT, ADAPTATION TO 



Colors of Nocturnal Animals. Nocturnal 

 animals supply another illustration of the 

 same rule [of protective coloration] in the 

 dusky colors of mice, rats, bats, and moles, 

 and in the soft-mottled plumage of owls and 

 goat-suckers which, while almost equally 



inconspicuous in the twilight, are such as to 

 favor their concealment in the daytime. 

 WALLACE Darwinism, ch. 8, p. 131. (Plum.) 



2418. NIGHT AND DAY, MYTHS 

 WOVEN AROUND Story of Little Red Rid- 

 ing-hood an Ancient Relic. Of all the na- 

 ture-myths of the world few are so widely 

 spread as those on this theme of night and 

 day, where with mythicjruth the devoured 

 victims were afterwards disgorged or set 

 free. The Zulu story-tellers describe the 

 maw of the monster as a country where 

 there are hills and houses and cattle and 

 people living, and, when the monster is cut 

 open, all the creatures come out from the 

 darkness; with a neat touch of nature, 

 which shows that the story-teller is think- 

 ing of the dawn, the cock comes out first, 

 crying "kukuluku! I see the world!" Our 

 English version of the old myth is the 

 nursery tale of Little Red Riding - hood, 

 but it is spoilt by leaving out the proper 

 end ( which German nurses have kept up 

 with better memory), that when the hunter 

 ripped up the sleeping wolf out came the 

 little damsel in her red satin cloak, safe and 

 sound. TYLOR Anthropology, ch. 15, p. 392. 

 (A., 1899.) 



2419. NIGHT A TIME OF ANXIETY 

 TO PRIMEVAL MAN What if Day Should 

 Return No More? Joyous Welcome to the 

 Rising Sun. The ancient poems of India 

 have even preserved for us the last echoes 

 of the fears of primeval man at the ap- 

 proach of night. The sun. the good sun, 

 has completely disappeared in the west; is 

 it certain that he will return to-morrow 

 morning in the east? If he should return 

 no more! no more light, no more heat; the 

 frozen night, gloomy night, covers the world ! 

 How shall we recover the lost fire? How re- 

 place the beneficent sun and his celestial 

 light? The stars from the height of the 

 heavens shed their melancholy light; the 

 moon pours out in the vacuities of the at- 

 mosphere that rosy, silvery light which dif- 

 fuses such a charm upon the sleep of Na- 

 ture; but this is not the sun, this is not the 

 day. . . . Ah, see the dawn, which 

 brightens slowly! Behold the light, behold 

 the day! Sun! King of the heavens, be 

 blessed ! Oh ! never forget to return ! 

 FLAMMARION Popular Astronomy, bk. i, ch. 

 2, p. 13. (A.) 



2420. NIGHT IN TROPICAL FOREST 



Discordant Cries Wide-spread Conflict 

 among Animals. After eleven o'clock, such 

 a noise began in the contiguous forest that 

 for the remainder of the night all sleep was 

 impossible. The wild cries of animals rung 

 through the woods. Among the many voices 

 which resounded together, the Indians could 

 only recognize those which, after short 

 pauses, were heard singly. There was the 

 monotonous, plaintive cry of the Aluates 

 (howling monkeys), the whining, flutelike 

 notes of the small sapajous, the grunting 

 murmur of the striped nocturnal ape 



