May 29, 18S5. 



♦ KNOWLEDGE 



4G5 



' Let Knowledge grow from more to more." — Alfbed Tknnyson. 



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The Editor is not responsible for the opinions of correspondents. 



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 AND DIRECTED ENTELOPE BE ENCLOSED. 



THE BUDDY ECLIPSED MOON. 



[1722] — I have referred to the commnnication of " Senex," in 

 vol. 6, page 324, and find that it confirms the observations I 

 described of the great variability of the kind and degree of 

 ninmioation of the eclipsed moon, and it goes further by showint^ 

 that there is not only a great difference between two eclipses, bat 

 also between the appearances presented by the same eclipse when 

 viewed from different places. We all agree in ascribing these 

 differences to variations in the condition of our atmosphere. Those 

 who attribute all the light on the eclipsed moon to refracted sun- 

 light describe the presence or absence of clouds on the terrestrial 

 horizon as the sole cause of the difference. According to my \-iew 

 of the cause of the ruddy element of the illumination, its variations 

 depend upon the varying transparency of our atmosphere to the 

 obscure heat rays. W. M.^ttied Willums. 



ULTRA-GAS. 



[1723] — I find that your reply (in the number for April 17) does 

 not completely clear np my difBcnIties. " I see nothing more in 

 the theorv of ultra-gas inconsistent with the Xewtonian theory 

 than I do in that of ordinary gas, in which the repulsion of the 

 molecules by heat overcomes their gravitating tendency ; or in the 

 fact that my holding a ball in my hand prevents it from reaching 

 the surface of the earth." 



But these two cases seem to me to show that the law (" gravity 

 varies inversely," &c.) is obviously open to exceptions, such as, 

 "unless some greater influence be opposed." ilaterial obstacles, 

 magnetism and heat, are influences to the point. Why not distance 

 also ? Have we any data for the behaviour of bodies reciprocally 

 at great distances from each other •' You continue (as would any 

 one) "that attraction, infijiitesimal as it is [that of the sun and 

 Arctnms] still exists." 



Snpposea body at the distance of Arcturus at rest, and all other 

 bodies destroyed except the sun ; would it move towards him ? I 

 think it is universally held that it would. I would ask on what 

 grounds this belief rests. Magnetism is a phenomenon analogous 

 to gravitation (only much stronger ?), yet the strongest magnet 

 will not attract the smallest particle of iron heyond a certain 

 dietance. The Conductor of Knowledge has remarked somewhere 

 that it is rash to suppose all bodies to be moving in curves ; that 

 probably many stars move in straight lines. I do not see how this 

 can be if there is even the very least pull on one of them from the 

 nearest larger body. If gravitation be indeed true for all distances, 

 then I do not see how any body can avoid an orbit. It will be 

 replied, that their rate of translation will overcome the pull of the 

 nearest body ; but there, again, seems another exception to the 

 universality — or, at least, the autocracy — of gravitation. 



" Do you think I shall get anything out of that cove ? " asks one 

 impostor of another. " I'es; he will give you in inverse proportion 

 to his penetration," is the reply, apparently affirmative, but really 

 negative. 



In certain cases there is no attraction, nor repulsion. Why 

 should not this be the case with all matter in some degree ? — the 

 repulsion existing only at distances beyond our use. 



I once asked Sir G. Airy what reason there is for concluding 

 that the velocity of light is everywhere uniform ? Ee replied that 



analogy leads us to believe that the ether is uniformly dense. I do 

 not see this at all. Why may not the neighbourhood of a liiijhly- 

 irritating body, like a star, change niatorially the mulululiou.s !■* 

 1 proposed that it should bo decided by the eclipses of Saturn's 

 satellites ; but 1 do not suppose this Ima been done. 



Up to 1S77, "all metals after fusion congeal again." -Vnal'^gy 

 would insist on this as a unircrsal law. But then gallium was dis- 

 covered, which is solid up to 80" F, then melts, but nvvcr beoiuea 

 solid again. Analogy would lead us to proclaim that all tho .satellites 

 are direct ; those of Uranus arc found to bo retrograde. 



Gravitation, beyond certain distanci^s, soems to mo to bo liko 

 minus quantities, or the nth power — convenient and iii'ci'-.sni'y 

 terms, but not real anywhuro out of Wonderland or " Flutlanci," 

 where they have but two dimensions. 



-As regards infinite greatness, 1 think the Conductor of K.now- 

 LEi>GE has remarked somewhere, that space ca7iuot bo infinite ; but 

 1 forget the reason given. And, as to infinite smallness, 1 think we 

 may conceive of a mathematical point (otherwise how domonstrato 

 anything ?), but not of anything less. Uai.i.vaud.s. 



[Is " Uallyards " quite sure that it was not a correspondent of 

 this journal, and not in the very least its Conductor, who categori- 

 cally denied the infinity of space ? Furthermore, seeing that a 

 mathematical point only defines position, and has no dimensions 

 whatever, it would be rather hard to conceive of anything lessl — 

 Ed.] 



SUNDIALS Foil MEANTIJIE. 



[1724] — " D. X. L." can plot the profile of each gnomon 

 thns : — 



Slender gnomon used from Christmas till June 15. Let n be 

 difference of time between apparent moon and 12h. 5m. ISa. More 

 bulging gnomon from June 21 till December 20. Let N be differ- 

 ence between apparent noon and llh.iJlm.5Ss. In both cases, 

 *t = the time in column-headed " Sidereal,'* &c., of p. 1 of each 

 mouth in " Nautical Almanac,' and D = Declination (same line of 

 same page). N-fs, or n + s must be put into degrees and minutes, 

 !.!'., quartered. For an abscissa of either profile, measured from its 



mid-length, take 



Tan D (l-.sin' .\-^») , 

 or Tan D (1 — sin"n-l- s) ; 

 and for the corresponding ordinate take 



Sin (N + .s), or sin (n + s). 

 Any year's Almanac will do. E. L. G. 



AX " EYE-OPENER." 



[1725] — To such of your readers as may be desirous of ascer- 

 taining, by practical trial, how wide their eyes can be made to open 

 under proper stimulation, I beg permission to indicate through 

 these columns, as a subject for their attention which will have that 

 effect in (I think) an agreeable and progressive manner, the 

 •article in an illustrated monthly scientific journal of comparatively 

 recent origin, entitled " The Basis of Perspective." I will not 

 spoil the experiment by any indications as to the nature of the sur- 

 prise which awaits them. 



I regret to say that bitter experience prevents my attaching my 

 name to this suggestion. I therefore subscribe myself Alias. 



ON TERMITES. 



[1726] — With reference to the remarks of " George Hann," No. 

 1628 of Knowledge, March 6, 1885, and " Commentator," No. 1638, 

 of March 13, I beg to state that I am in no way a believer in the 

 doctrines of natural selection or evolution. 



I lately propounded a difficulty to the Editor of Knowledge, but 

 he didn't publish it. It was this : — By what process of evolution 

 or natural selection is the dumba (two-tailed) sheep of Afghanistan 

 matured which cannot reproduce its kind without the assistance of 

 man? 



But, abandoning "nos moutons," "revenons a nos termites;" 

 my paper was by no means exhaustive ; for instance, I was silent 

 on the fact that the flight is the perfection of the insect ; contact 

 with atmospheric air, and especially absorption of oxygen and 

 perhaps moisture complete the development of the termite and 

 prepare the survivors for the process of reproduction. 



Recollect that in the flight there has been no feeding or alighting, 

 the male, after impregnation of a female, returns underground to 

 die ; and the fertilised female has no one to feed her, and no means, 

 apparent to us, of procuring food, and she must wait until the 

 developed workers from the eggs she is still to lay can undertake 



