42 



♦ KNO^A^LEDGE ♦ 



[December 1, 1887. 



mous velocity through space, it is not an oscillating but a 

 continuous motion that has to be determined. In a year 

 this motion may be less (and curiously very much less) than 

 the annual swaying motion of the nearest star. But in the 

 course of many years it becomes measurable or even (in the 

 astronomical sense) considerable. We speak of the astro- 

 nomical sense, meaning the way in which an astronomer 

 considers displacements, which to ordinary observation are 

 altogether inappreciable. With the telescope, magnifying 

 such displacements several hundredfold, and also supplying 

 the most delicate means of testing displacement, a change of 

 place equal to the hundredth part of the moon's seeming 

 diameter, instead of being barely discernible (as it certainly 

 would be to the unaided vision) is a phenomenon altogether 

 obvious and startling. 



Even so, however, by far the greater number of the stars 

 move so slowly on the heavens that the lifetime of a single 

 observer would be insufficient for an exact determination of 

 a star's rate of (apparent) motion. There are some few stars 

 indeed which are moving with abnormal rajiidity ; and these 

 could have their rates determined in twenty or thirty years 

 with great accuracy. Yet even among these the amount of 

 change in an ordinary lifetime seems surprising small. For 

 instance, the star which moves most rapidly of all — not a 

 bright and conspicuous star as might be supposed, but a star 

 so faint that it has not been thought worth while to give it 

 a name in ordinary star lists — moves in sixty years over a 

 distance less than one-fourth of the moon's apparent dia- 

 meter. So that if an observer twenty years old noted the 

 place of this star, and in his eightieth year observed it again, 

 it would be that seemingly insignificant arc which he would 

 have to measure — not to recognise such and such a dis- 

 placement, but to measure its amount with accuracy. 



Of the real rates of stellar travelling we can form no exact 

 ideas, simply because the stars' distances are unknown. 

 There is a method by which the rates of stellar approach and 

 recession can theoretically be determined ; but as yet it has 

 not been applied with anything like exactness. 



It ap]iears proliable that the average rate of stellar travel 

 is about twenty miles per second, a wonderful velocity if we 

 consider that each star is a sun like our own, and that, like 

 the rest, our sun, with his family of planets, is travelling 

 with kindred velocity through space. 



By Richaed A. Proctor. 



I WRITE my Gossip for this month " by Susquehanna's side," 

 at Wilkes-Barre, IPennsylvania, and in a hotel called "The 

 Wyoming Centre." As I write, a wretched steam-whistle 

 is sounding out the signal demanded by law when steamers 

 on a river sight each other; but otherwise, as the shades of 

 evening close over the scene, it is easy to conceive that in 

 the days of the imaginary " (Jertrude " the valley of the 

 Susquehanna looked much as it appears before me now, save 

 for a very modern and business-like bridge just within sight 

 on the right. 



* * * 



The story is a touching one as Campbell tells it. It is a 

 slight matter that Wyoming is never pronounced Wy'oming, 

 as the rhythm requires in the line 



On Susquehanna's side fair Wyoming ; 



but always Wyoming. Unhappily, there is a much more 

 serious detail in which reality and the Gertrude story are at 

 issue. Campbell remarks, and might with fail' reason have 

 remarked, had he ever visited the Wyoming Valley, that 



" though the wild flower on the crumbled wall " and " ruined 

 homes a sad remembrance bring " (so nearly as my memory 

 serves me) " of what thy gentle people did beftd, yet thou," 

 meaning Wyoming, "' wert once the loveliest land of all." 

 It rather destroys the charm of the legend to learn, as is 

 well known here " by Susquehanna's side," th.at of the three 

 hundred and more who went forth to attack the Indians on 

 that sad occasion, barely thirty were sober — all the sober 

 ones, by the way, escaping with their lives. The descend- 

 ants of the old settlers are a little sore when the real 

 inwardness of the old Wyoming story is mentioned, though 

 many of them mu.st of course be descended from the sober 

 thirty. 



A CORRESPONDENT sends me a cutting from the Spectator, in 

 which a certain explosive is described which can produce 

 its full efl'ects without any heavy substance like cannon, 

 mortars, or the like, from which it need be discharged. 

 From a paper tubing it would be as effective as from a 

 twenty- ton gun. Hence certain direful effects are anticipated 

 for nations like the Swiss, who have hitherto owed their 

 safety solely to the difficulty of conveying artillery into 

 their mountain fa.stnesses. My correspondent asks whether 

 such an explosive and such singularly " light " artillery are 

 possibilities. They will become so when " action and 

 reaction " cease to be equal and opposite; that is, never. 



* * * 



Another correspondent asks me whether I consider the 

 influence of the moon on the weather worth the attention 

 given to it in a recent number of Longman's Magazine. 

 Since I consider the influence of the moon on the weather 

 as nearly as possible nil, it should hardly be necessary for 

 me to say that I do not. Regarded as superstitions be- 

 longing to the old time when the moon shared with the sun 

 and planets very potent influence over man, the fancies 

 about the moon's weather significance are quaint and 

 amusing enough. But it would be a waste of time to con- 

 sider whether after all there may not be some meaning 

 in them, since, without a single exception, they bear the 

 clearest traces of their unscientific origin. 



* * * 



There is one lunar fancy only which has (though its inven- 

 tors knew nothing of this) a quasi-scientific interpi'ttation. I 

 refer to the notion that if the old moon is seen very distinctly 

 in the new moon's arms wet weather will probably follow. 

 As I pointed out many years ago, illumination of the moon 

 by the earth, when, the moon being " new," the earth is 

 " full " to her, must be to some degree greater when the 

 earth's sunward face is cloud-covered — and as that face lies 

 west of the observer's station when the new moon is seen in 

 the west (the sun having recently set) we have in the bright- 

 ness of the old moon in the new moon's arms a certain 

 indication of cloudy skies west of the observer, whence 

 usually weather travels. But those who know how per- 

 sistently the old moon is seen clearly and strongly, even to 

 the time of the moon's first quarter, in countries which have 

 clear skies, while in hazy climes the old moon is seldom seen, 

 must feel well assured that the distinctness of the old moon 

 depends fiir more on clearness of sky than on any increase in 

 the amount of " earth shine." 



* * * 



A CORRESPONDENT would like to see that explanation of 

 an ice yacht's travelling faster than the wind, to which 

 reference is made in my article on the curve in base-ball. 

 In one of the first few numbers of Knowledge such an 

 explanation is given. It may suffice to note here that with 

 a strong beam wind, if an ice yacht travels no faster than 



