631 



SCIENTIFIC SIDE-LIGHTS 



skill 

 sleep 



shall see later, may owe something to the 

 mysterious source of the phenomena [me- 

 teors] already alluded to. LANGLEY The 

 New Astronomy, ch. 6, p. 179. (H. M. &. 

 Co., 1896.J 



3125. SKY COMBINES ALL COLORS 



Blue Not Sole, but Predominant Small- 

 est Particles Reflect Smallest Waves. In 

 the case of water, for example, a pebble will 

 intercept and reflect a larger fractional part 

 of a ripple than of a larger wave. We have 

 now to imagine light-undulations of differ- 

 ent dimensions, but all exceedingly minute, 

 passing through air laden with extremely 

 small particles. It is plain that such par- 

 ticles, tho scattering portions of all the 

 waves, will exert their most conspicuous 

 action upon the smallest ones ; and that the 

 color-sensation answering to the smallest 

 waves in other words, the color blue will 

 be predominant in the scattered light. This 

 harmonizes perfectly with what we ob- 

 serve in the firmament. The sky is blue, 

 but the blue is not pure. On looking at the 

 sky through a spectroscope we observe all 

 the colors of the spectrum; blue is merely 

 the predominant color. TYNDALL Fragments 

 of Science, vol. i, ch. 5, p. 138. (A., 1897.) 



3126. SLAVERY DEGRADES THE 



MASTERS Slave-making Ants Powerless to 

 Help or Feed Themselves. Polyergus rufes- 

 cens present a striking lesson of the degra- 

 ding tendency of slavery, for these ants have 

 become entirely dependent on their slaves. 

 Even their bodily structure has undergone 

 a change; the mandibles have lost their 

 teeth, and have become mere nippers, deadly 

 weapons, indeed, but useless except in war. 

 They have lost the greater part of their in- 

 stincts: their art, that is, the power of 

 building; their domestic habits, for they 

 show no care for their own young, all this 

 being done by the slaves; their industry 

 they take no part in providing the daily 

 supplies; if the colony changes the situation 

 of its nest, the masters are all carried by 

 the slaves on their backs to the new one; 

 nay, they have even lost the habit of feed- 

 ing. Huber placed thirty of them with 

 some larvae and pupae and a supply of honey 

 in a box. "At first," he says, "they ap- 

 peared to pay some little attention to the 

 larvae; they carried them here and there, 

 but presently replaced them. More than one- 

 half of the Amazons died of hunger in less 

 than two days. They had not even traced 

 out a dwelling, and the few ants still in 

 existence were languid and without strength. 

 I commiserated their condition, and gave 

 them one of their black companions. This 

 individual, unassisted, established order, 

 formed a chamber in the earth, gathered 

 together the larvae, extricated several young 

 ants that were ready to quit the condition 

 of pupae, and preserved the life of the re- 

 maining Amazons." AVEBURY Ants, Bees, 

 and Wasps, ch. 4, p. 82. (A., 1900.) 



3127. "SLEEP" OF PLANTS Pur- 

 pose Not the Same as in Sleep of Animals. 

 The so-called sleep of leaves is so conspicu- 

 ous a phenomenon that it was observed as 

 early as the time of Pliny; and since Lin- 

 naeus published his famous essay, " Somnus 

 Plantarum," it has been the subject of sev- 

 eral memoirs. Many flowers close at night, 

 and these are likewise said to sleep; but we 

 are not here concerned with their move- 

 ments, for altho effected by the same mecha- 

 nism as in the case of young leaves, namely, 

 unequal growth on the opposite sides (as 

 first proved by Pf eff er ) , yet they differ 

 essentially in being excited chiefly by changes 

 of temperature instead of light, and in 

 being effected, as far as we can judge, for 

 a .different purpose. Hardly any one sup- 

 poses that there is any real analogy between 

 the sleep of animals and that of plants, 

 whether of leaves or flowers. DARWIN Pow- 

 er of Movement in Plants, ch. 6, p. 283. 

 (A., 1900.) 



3128. SLEEP THE REPOSE OF THE 

 BRAIN Rest of Voluntary and Involuntary 

 Muscles Compared. All parts of the body 

 which are the seat of active change require 

 periods of rest. The alternation of work 

 and rest is a necessary condition of their 

 maintenance and of the healthy perform- 

 ance of their functions. These alternating 

 periods, however, differ much in duration in 

 different cases; but, for any individual in- 

 stance, they preserve a general and rather 

 close uniformity. Thus, as before mentioned, 

 the periods of rest and work, in the case 

 of the heart, occupy, each of them, about 

 half a second; in the case of the ordinary 

 respiratory muscles the periods are about 

 four or five times as long. In many cases, 

 again (as of the voluntary muscles during 

 violent exercise) , while the periods during 

 active exertion alternate very frequently, 

 yet the expenditure goes far ahead of the 

 repair, and to compensate for this an after- 

 repose of some hours becomes necessary, 

 the rhythm being less perfect as to time 

 than in the case of the muscles concerned 

 in circulation and respiration. 



Obviously, it would be impossible that 

 in the case of the brain there should be short 

 periods of activity and repose, or in other 

 words, of consciousness and unconsciousness. 

 The repose must occur at long intervals, and 

 it must therefore be proportionately long. 

 Hence the necessity for that condition which 

 we call " sleep," a condition which, seeming 

 at first sight exceptional, is only an unusual- 

 ly perfect example of what occurs, at vary- 

 ing intervals, in every actively working por- 

 tion of our bodies.^ BAKER Handbook of 

 Physiology, vol. ii, ch. 18, p. 135. (W. W., 

 1885.) 



3129. Withdrawal of 



Blood Leaving Brain Anemic Parallel of 

 Swooning. A temporary abrogation of the 

 functions of the cerebrum imitating sleep 

 may occur, in the case of injury or disease, 



