Variety 

 Vegetation 



SCIENTIFIC SIDE-LIGHTS 



730 



which were aboriginally alike in an early 

 progenitor in each of these classes. 

 DARWIN Origin of Species, ch. 15, p. 494. 

 (Burt.) 



3618. VARIETY OF COLOR AMONG 



THE STARS -Double Stars of Complementary 

 Colors. A careful examination of the bright 

 double stars . . . teaches that, besides 

 white, all the colors of the solar spectrum 

 are to be found in the double stars, but 

 that the principal star, whenever it is not 

 white, approximates in general to the red 

 extreme ( that of the least refrangible rays ) , 

 but the companion to the violet extreme 

 (the limit of the most refrangible rays). 

 The reddish stars are twice as frequent as 

 the blue and bluish ; the white are about two 

 and a half times as numerous as the red 

 and reddish. It is moreover remarkable 

 that a great difference of color is usually 

 associated with a corresponding difference 

 in brightness. In two cases in Bootis and 

 y Leonis which, from their great bright- 

 ness, can easily be measured by powerful 

 telescopes, even in the daytime, the former 

 consists of two white stars of the third 

 and fourth magnitudes, and the latter of a 

 principal star of the second, and of a com- 

 panion of the 3.5th magnitude. This is usual- 

 ly called the brightest double star of the 

 northern hemisphere, whereas a Centauri 

 and <* Crucis, in the southern hemisphere, 

 surpass all the other double stars in bril- 

 liancy. . . . "This superb double star 

 (a Centauri) is beyond all comparison 

 the most striking object of the kind in 

 the heavens, and consists of two individ- 

 uals, both of a high ruddy or orange color, 

 tho that of the smaller is of a somewhat 

 more somber and brownish cast." ( Sir John 

 Herschel, " Observations at the Cape of Good 

 Hope," p. 300.) HUMBOLDT Cosmos, vol. iii, 

 p. 209. (H., 1897.) 



3619. VARIETY OF COLOR IN 

 DEEP-SEA ECHINODERMS Compared to 

 Autumn Leaves. It is impossible to account 

 for [the] extraordinary variety of color in 

 the deep-sea echinoderms. It is hardly prob- 

 able that it can be protective or warning in 

 function, and it is difficult to suppose that 

 it is due to any peculiar excretory process. 

 Whether it is due in any way to the influ- 

 ence of the environment, or, like the color 

 of autumn leaves, to the chemical degenera- 

 tion of colors that in the shallow-water 

 ancestry were functional, are problems that 

 must be left for the future to decide. 

 HICKSON Fauna of the Deep Sea, ch. 4, p. 64. 

 (A., 1894.) 



3620. VARIETY OF MOVEMENT 

 OF COMETS -Celestial Visitors Captives of 

 Sun's Attraction. Four principal charac- 

 teristics distinguish comets from planets: 

 (1) Their nebulous aspect and their tails, 

 often considerable; (2) the length of the 

 elliptical orbits which they describe; (3) 

 the inclination of these orbits, which, instead 

 of lying in the plane of the ecliptic, or at 



least in the zodiac, like those of the planets 

 in general, are inclined at all degrees up to 

 a right angle, and sometimes carry the 

 comets to the polar constellations: (4) the 

 directions of their motions, which, instead of 

 being performed in the same direction as 

 those of planets, are, some direct, others 

 retrograde, and appear to be strangers to 

 any unity of plan. From these circum- 

 stances the certain conclusion follows that 

 comets have not the same origin as the 

 planets, that they did not originally belong 

 to the solar system, that they travel through 

 immensity, that they may be transported 

 from one sun to another (from star to star) , 

 and that those which revolve round our sun 

 have been caught in their passage by his at- 

 traction, having had their course curved and 

 closed by the influence of the planets of our 

 system. FLAMMARION Popular Astronomy, 

 bk. v, ch. 2, p. 489. (A.) 



3621. VARIETY OF NATURE Au- 

 rora Ranges from Low Elevation Up to Hun- 

 dreds of Miles. From all this evidence we 

 are entitled to conclude that the altitude 

 of polar auroras varies within very wide 

 limits, and that, in spite of the opinion of 

 certain authors, it is certainly possible to 

 observe auroral manifestations quite near 

 the surface of the earth. . . . 



But let us distinguish. In mean latitudes, 

 in France and Central Europe, all measure- 

 ments of the height of the aurora have al- 

 ways given very high numbers [by some 

 observers in some instances estimated at 

 more than 500 miles]. . . . It is only 

 in latitudes above the 55th or 60th parallel 

 that auroras are undoubtedly found at a 

 much lower level, and sometimes even quite 

 near the surface of the earth. It seems, 

 then, lawful to assume that the mean height 

 at which the aurora is produced diminishes 

 as we approach the poles. Perhaps exceed- 

 ing 100 kilometers (60 miles) in low lati- 

 tudes, it descends to some tens of miles in 

 the arctic regions, and may even be quite 

 near the ground. ANGOT Aurora Borealis, 

 ch. 4, p. 68. (A., 1897.) 



3622. 



Close Observation 



Finds Endless Differences Shepherd Knows 

 Individual Sheep. If we look about us in 

 a forest consisting of only a single species 

 of tree, for example, of beech, we shall cer- 

 tainly not find in the whole forest two trees 

 of this kind which are absolutely identical 

 or perfectly equal in the form of their 

 branches, the number of their branches, and 

 leaves, blossoms, and fruits. Special differ- 

 ences occur everywhere, just as in the case 

 of men. There are no two men who are 

 absolutely identical, perfectly equal in size, 

 in the formation of their faces, the number 

 of their hairs, their temperament, character, 

 etc. The very same is true of individuals 

 of all the different species of animals and 

 plants. It is true that in most organisms 

 the differences are very trifling to the eye 

 of the uninitiated. Everything here essen- 



