651 



SCIENTIFIC SIDE-LIGHTS 



Stars 

 Steam-jets 



divine better the distant life which is in 

 motion round each of these brilliant fires 

 burning in infinitude. . . . 



Scintillation is a phenomenon caused 

 partly by the intrinsic light and partly by 

 the state of our atmosphere. 



The stars which scintillate most are the 

 white stars, like Sirius, Vega, . . . etc. 

 [86 variations per second]. The stars 

 which scintillate least are the orange or red 

 stars, like Antares, Aldebaran, Arcturus, 

 etc. [56 variations per second]. 

 There is thus a certain correspondence 

 between the scintillation of a star and its 

 physical constitution. 



Our atmosphere plays a considerable part 

 in the scintillation; the lower a star is, the 

 more it scintillates; the scintillation is pro- 

 portional to the product which we obtain 

 by multiplying the thickness of the layer of 

 air traversed by the luminous ray emanating 

 from the star by the astronomical refraction 

 for the altitude at which it is observed. 



The scintillation is more pronounced as 

 the cold is greater; it is stronger in winter 

 than in summer a fact which may be no- 

 ticed by everybody. FLAMMABION Popular 

 Astronomy, bk. vi, ch. 6, p. 606. (A.) 



3222. STARS WITHDRAWN FROM 

 NORTHERN SKIES Change in the Heavens. 

 It was not more than 2,900 years before 

 our era that the Cross ( the Southern Cross ) 

 became invisible in northern Germany. The 

 constellation had ascended as far as the 

 tenth degree above the horizon. When it 

 disappeared from the Baltic skies, the pyra- 

 mid of Cheops had already stood five hun- 

 dred years. The shepherd nation of the 

 Hyksos invaded Egypt seven hundred years 

 later. The past becomes apparently less re- 

 mote when we can measure it by reference 

 to memorable events. HUMBOLDT Cosmos, 

 vol. ii, pt. ii, p. 290. (H., 1897.) 



3223. STARS WITHOUT LIGHT 



Non-luminous Bodies May Have Brilliant 

 Satellites. The belief in the existence of 

 non-luminous stars was diffused even among 

 the ancient Greeks, and especially in the 

 earliest ages of Christianity. It was as- 

 sumed that among the fiery stars which 

 are nourished by the celestial vapors there 

 revolve certain other earthlike bodies, which, 

 however, remain invisible to us. The total 

 extinction of new stars, especially of those 

 so carefully observed by Tycho Brahe and 

 Kepler in Cassiopeia and Ophiuchus, appears 

 to corroborate this opinion. Since it was 

 at the time conjectured that the first of 

 these stars had already twice appeared, and 

 that, too, at intervals of nearly 300 years, 

 the idea of annihilation and total extinction 

 naturally gained little or no credit. The 

 immortal author of the " Mgcanique Celeste " 

 [Laplace] bases his conviction of the exist- 

 ence of non-luminous masses in the universe 

 on these same phenomena of 1572 and 1604: 

 " These stars, that have become invisible 

 after having surpassed the brilliancy of Ju- 



piter, have not changed their place during 

 the time of their being visible." (The lumi- 

 nous process in them has simply ceased.) 

 " There exist, therefore, in celestial space 

 dark bodies of equal magnitudes, and prob- 

 ably in as great numbers as the stars." So 

 also Madler, in his " Untersuchungen iiber 

 die Fixstern-Systeme," says : " A dark body 

 might be a central body;~it might, like our 

 own sun, be surrounded in its immediate 

 neighborhood only by dark bodies like our 

 planets. The motions of Sirius and Procyon, 

 pointed out by Bessel, force us to the as- 

 sumption that there are cases where lumi- 

 nous bodies form the satellites of dark 

 masses." HUMBOLDT Cosmos, vol. iii, p. 187. 

 (H., 1897.) 



3224. STATES, MENTAL, RESULT 

 IN PHYSICAL ACTION Interdependence of 

 Body and Mind. The psychologist is forced 

 to be something of a nerve-physiologist. 

 Mental phenomena are not only condi- 

 tioned a parte ante by bodily processes; 

 but they lead to them a parte post. That 

 they lead to acts is of course the most 

 familiar of truths, but I do not merely 

 mean acts in the sense of voluntary and 

 deliberate muscular performances. Mental 

 states occasion also changes in the cali- 

 ber of blood-vessels, or alteration in the 

 heart-beats, or processes more subtle still, 

 in glands and viscera. If these are taken 

 into account, as well as acts which follow 

 at some remote period because the mental 

 state was once there, it will be safe to lay 

 down the general law that no mental modi- 

 fication ever occurs which is not accom- 

 panied or followed by a bodily change. The 

 ideas and feelings, e. g. which these present 

 printed characters excite in the reader's 

 mind not only occasion movements of his 

 eyes and nascent movements of articula- 

 tion in him, but will some day make him 

 speak, or take sides in a discussion, or give 

 advice, or choose a book to read, differently 

 from what would have been the case had 

 they never impressed his retina. JAMES 

 Psychology, vol. i, ch. 1, p. 5. (H. H. & 

 Co., 1899.) 



3225. STEAM-JETS IN NATURE 



Volcanoes the Vents for Imprisoned Waters. 

 If water be subjected to sufficiently great 

 pressure it may be raised to a very high 

 temperature and still retain its liquid con- 

 dition. When this pressure is removed, 

 however, the whole mass passes at once into 

 the condition of steam or water-gas, and 

 the gas thus formed at high temperatures 

 has a proportionably high tension. In a 

 Papin's digester water confined in a strong 

 vessel is raised to temperatures far above 

 its ordinary boiling-point, and from any 

 opening in such a vessel the steam escapes 

 with prodigious violence. Now, at consid- 

 erable depths beneath the earth's surface, 

 and under the pressure of many hundreds 

 or thousands of feet of solid rock, water 

 still retaining its liquid condition may be- 



