637 



SCIENTIFIC SIDE-LIGHTS 



Pound 

 Space 



waves, from eighteen to thirty-six inches 

 long. The rustling of silken skirts excites 

 little curls in the air, each instrument in 

 the orchestra emits its peculiar waves, and 

 all these systems expand spherically from 

 their respective centers, dart through each 

 other, are reflected from the walls of the 

 room, and thus rush backwards and for- 

 wards until they succumb to the greater 

 force of newly generated tones. 



Altho this spectacle is veiled from the 

 material eye, we have another bodily organ, 

 the ear, especially adapted to reveal it to 

 us. This analyzes the interdigitation of the 

 waves, which in such a case would be far 

 more confused than the intersection of 

 the water undulations, and separates the 

 several tones which compose it, and dis- 

 tinguishes the voices of men and women, 

 nay, even of individuals, and of the peculiar 

 qualities of tone given out by each instru- 

 ment, the rustling of the dresses, the foot- 

 falls of the walkers, and so on. HELMHOLTZ 

 On the Physiological Causes of Harmony in 

 Music (Popular Lectures, ser. i, p. 79). 

 (Translated for Scientific Side-Lights.) 



3155. SOURCE OF THE SUN'S HEAT 

 By Combustion It Would Burn Out in 

 Three Thousand Years. On earth the proc- 

 esses of combustion are the most abundant 

 source of heat. Does the sun's heat origi- 

 nate in a process of this kind? To this 

 question we can reply with a complete and 

 decided negative, for we now know that the 

 sun contains the terrestrial elements with 

 which we are acquainted. Let us select from 

 among them the two which, for the smallest 

 mass, produce the greatest amount of heat 

 when they combine ; let us assume that the 

 sun consists of hydrogen and oxygen, mixed 

 in the proportion in which they would unite 

 to form water. The mass of the sun is 

 known, and also the quantity of heat pro- 

 duced by the union of known weights of 

 oxygen and hydrogen. Calculation shows 

 that under the above supposition the heat 

 resulting from their combustion would be 

 sufficient to keep up the radiation of heat 

 from the sun for 3,021 years. That, it is 

 true, is a long time, but even profane his- 

 tory teaches that the sun has lighted and 

 warmed us for 3,000 years, and geology puts 

 it beyond doubt that this period must be 

 extended to millions of years. Known chem- 

 ical forces are thus so completely inadequate, 

 even on the most favorable assumption, to 

 explain the production of heat which takes 

 place in the sun, that we must quite drop 

 this hypothesis. HELMHOLTZ Popular Lec- 

 tures, ser. ii, lect. 4, p. 178. (L. G. & Co., 

 1898.) 



3156. SOURCE OF THE WINDS 

 Circulation in Doorway of Heated Room 

 Currents of Aerial Ocean. From the heat 

 of the sun our winds are all derived. We 

 live at the bottom of an aerial ocean, in a 

 remarkable degree permeable to the solar 

 rays, and but little disturbed by their direct 



action. But those rays, when they fall upon 

 the earth, heat its surface, and when they 

 fall upon the ocean they provoke evapora- 

 tion. The air in contact with the surface 

 shares its heat, is expanded, and ascends 

 into the upper regions of the atmosphere, 

 while the vapor from the ocean also ascends, 

 because of its lightness, carrying air along 

 with it. Where the rays fall vertically on 

 the earth, that is to say, between the tropics, 

 the heating of the surface is greatest. Here 

 aerial currents ascend and flow laterally, 

 north and south, towards the poles, the 

 heavier air of the polar regions streaming 

 in to supply the place vacated by the light 

 and warm air. Thus we have incessant 

 circulation. A few days ago, in the hot 

 room of a Turkish bath, I held a lighted 

 taper in the open doorway, midway between 

 top and bottom. The flame rose vertically 

 from the taper. When placed at the bot- 

 tom the flame was blown violently inwards; 

 when placed at the top, it was blown vio- 

 lently outwards. Here we had two currents, 

 or winds, sliding over each other, and mov- 

 ing in opposite directions. Thus, also, as 

 regards our hemisphere, a current from the 

 equator sets in towards the north and flows 

 in the higher regions of the atmosphere, 

 while, to supply its place, another flows 

 towards the equator in the lower regions 

 of the atmosphere. These are the upper and 

 the lower trade winds. TYNDALL Heat a 

 Mode of Motion, lect. 8, p. 208. (A., 1900.) 



3157. SPACE FILLED WITH LU- 

 MINIFEROUS ETHER No Empty Spot- 

 Belief that Other Inhabited Worlds Exist. 

 As far as our knowledge of space extends, 

 we are to conceive it as the holder of the 

 luminiferous ether, through which are in- 

 terspersed, at enormous distances apart, the 

 ponderous nuclei of the stars. Associated 

 with the star that most concerns us we have 

 a group of dark planetary masses revolving 

 at various distances round it, each again 

 rotating on its own axis; and, finally, as- 

 sociated with some of these planets we have 

 dark bodies of minor note the moons. 

 Whether the other fixed stars have similar 

 planetary companions or not is to us a mat- 

 ter of pure conjecture, which may or may 

 not enter into our conception of the uni- 

 verse. But probably every thoughtful per- 

 son believes, with regard to those distant 

 suns, that there is in space something be- 

 sides our system on which they shine. 

 TYNDALL Fragments of Science, vol. i, ch. 1, 

 p. 5. (A., 1897.) 



3158. SPACE IMPENETRABLE 



Giant Telescopes of Herschel and Rosse 

 Leave Star Depths Yet Unfathomed. It has 

 been said that with the telescopes with 

 which the Herschels have surveyed the 

 depths of heaven twenty millions of stars 

 are visible. But these telescopes do not 

 penetrate to the limits of the star system. 

 In certain parts of the Milky Way Sir W. 

 Herschel not only failed to penetrate the 



