Ill 



SCIENTIFIC SIDE-LIGHTS 



Coloration 

 Combinatioi 







an historically proved change of color, for it 

 has at present a perfectly white light. A 

 great physical revolution must therefore 

 have occurred at the surface or in the photo- 

 sphere of this fixed star. HUMBOLDT Cos- 

 mos, vol. iii, p. 130. (H., 1897.) 



547, 



Variety and Con- 



trast of Instances of Double, Triple, and 

 Multiple Stars. Stars have also been 

 noticed which, instead of showing a white 

 or golden light, as is generally the case, are 

 colored with the most vivid tints, such as 

 those of the emerald, sapphire, ruby, topaz, 

 garnet, and the finest of our precious stones. 

 The telescope has discovered a large number 

 which, instead of being single, as they ap- 

 pear to the naked eye, are double, composed 

 of two stars close together which turn round 

 each other in revolutions which we have al- 

 ready been able to calculate, and which in- 

 clude the most varied periods, from a few 

 years to several centuries and even thou- 

 sands of years. Sometimes the system is 

 triple : a bright star is seen accompanied by 

 two little companions, and while these two 

 revolve round each other, they move to- 

 gether and revolve round the large one. It 

 is among these multiple systems that we 

 find the most wonderful contrasts of colors. 

 The science is already so far advanced in 

 this respect that I have been able to form a 

 catalog of nearly 1,000 double stars in 

 certain motion, and to construct a chart of 

 more than 10,000 double stars which have 

 been discovered. FLAMMARION Popular As- 

 tronomy, bk. vi, ch. 3, p. 580. (A.) 



548. COLORS OF THIN PLATES 



Films of Any Kind Illustrate Newton 

 Blowing Soap-bubbles. This subject [of 

 the interference of light-waves] may be il- 

 lustrated by the class of phenomena which 

 first suggested the undulatory theory to the 

 mind of Hooke. These are the colors of thin 

 transparent films of all kinds, known as the 

 colors of thin plates. In this relation no 

 object in the world possesses a deeper scien- 

 tific interest than a common soap-bubble. 

 And here let me say emerges one of the diffi- 

 culties which the student of pure science en- 

 counters in the presence of "practical" com- 

 munities like those of America and Eng- 

 land; it is not to be expected that such 

 communities can entertain any profound 

 sympathy with labors which seem so far re- 

 moved from the domain of practise as many 

 of the labors of the man of science are. 

 Imagine Dr. Draper spending his days in 

 blowing soap-bubbles and in studying their 

 colors ! Would you show him the necessary 

 patience, or grant him the necessary sup- 

 port ? And yet, be it remembered, it was thus 

 that minds like those of Boyle, Newton, and 

 Hooke were occupied; and that on such ex- 

 periments has been founded a theory the is- 

 sues of which are incalculable. I see no 

 other way for you, laymen, than to trust the 

 scientific man with the choice of his inquir- 

 ies; he stands before the tribunal of his 



peers, and by their verdict on his labors you 

 ought to abide. TYNDALL Lectures on Light, 

 lect. 2, p. 65. (A., 1898.) 



549. Interference of Light- 

 waves Illustrated Prismatic Colors of a 

 Film of Spirit of Turpentine on Water. 

 Take with you a little bottle of spirit of tur- 

 pentine, and pour it into one of your coun- 

 try ponds. You will then see the flashing of 

 those colors over the surface of the water. 

 On a small scale we produce them thus: A 

 common tea-tray is filled wfth water, be- 

 neath the surface of which dips the end of a 

 pipette. A beam of light falls upon the 

 water, and is reflected by it to the screen. 

 Spirit of turpentine is poured into the 

 pipette; it descends, issues from the end in 

 minute drops, which rise in succession to 

 the surface. On reaching it, each drop 

 spreads suddenly out as a film, and, glowing 

 colors immediately flash forth upon the 

 screen. The colors change as the thickness 

 of the film changes by evaporation. They 

 are also arranged in zones, in consequence 

 of the gradual diminution of thickness from 

 the center outwards. [See COLORS OBTAINED 

 FROM THIN FILMS; LIGHT, DOUBLE REFLEC- 

 TION OF, PLATES; etc.] TYNDALL Lectures 

 on Light, lect. 2, p. 67. (A., 1898.) 



550. COLORS RESULTING FROM 

 MOLECULAR ARRANGEMENT OF SUB- 

 STANCES It is the molecular arrange- 

 ment of reflecting or transparent substances 

 which gives rise to the different reflections 

 of light that is to say, the colors. A slight 

 difference produces here a blue eye, pensive 

 and thoughtful, there a brown eye with half- 

 hidden flames, there a look dull and dis- 

 tasteful. The dazzling rose which blooms in 

 the flower-garden receives the same light as 

 the lily, the buttercup, the cornflower, or the 

 violet; molecular reflection produces all the 

 difference; and we might even say, without 

 metaphor, that objects are of all colors ex- 

 cept that which they appear. Why is the 

 meadow green? Because it keeps all except 

 the green, which it does not want, and sends 

 back. White is formed by the reflective na- 

 ture of an object which keeps nothing and 

 returns all ; black, by a surface which keeps 

 all and sends back nothing. FLAMMARION 

 Popular Astronomy, bk. iii, ch. 7, p. 321. 

 (A.) 



551. COMBINATION MAY PERISH 



Substance or Agent Must Remain. There is 

 no existing order no present combination 

 of matter or of force which we cannot con- 

 ceive coming to an end. But when that end 

 is come, we cannot conceive but that some- 

 thing must remain if it be nothing else 

 than that by which the ending was brought 

 about. ARGYLL Unity of Nature, ch. 4, p. 

 85. (Burt.) 



552. COMBINATION OF INTELLI- 

 GENCE The Republic of the Stars By Elec- 

 tricity the Astronomer Looks from All Parts 

 of the World at Once. Modern facilities of 

 communication have helped to impress more 



