May 1, 1900.] 



KNOWLEDGE. 



109 



proportion of their total light " by atmospheric absorp- 

 tion and similar causes. Mav I ask by what experiments 

 or observations this is proved ' All the photometries 

 with which I am acquainted proceed on the opposite 

 principle. In none of them is a different estimate made 

 for atmospheric absorption in the case of bright and 

 faint stars. Prof. Prit-chard's photometer depends on 

 the thickness of a plat« of neutral-tinted glass which is 

 required to extinguish the light of the stai-. It would 

 fail if there 'was a more rapid (pi-oportional) extinction 

 in the case of faint stai-s than of bright ones. 



When a star is near the limit of vision a small re- 

 duction in its light rendei-s it imperceptible as a separate 

 object. A tield-ghiss. however, will suffice to di-scover it. 

 With a further reduction in the light a telescope would 

 be required, and we should afterwai-ds have to discard 

 our first telescope and use a more powerful one. But 

 can anvone suppose that in these cases it pix)duces no 

 effect at all unless it is sepai'ately visible? Mr. 

 Anderson disavows this argument, however, and, there- 

 fore, I need not discuss it. 



Considering the great number of different places at 

 which observations are now made, and the fact that star- 

 gauges aie usually made at the most favourable time 

 for observation, I can hardly believe that there are 

 any stars brighter than sav the 1 2th magnitude which 

 have remained undiscovered because they were always 

 too near the horizon to be visible with a telescope cal- 

 culated to show all stai-s down to the 14th magnitude. 

 (Of course the visibility or invisibility of faint stars de- 

 pends entirelv on the instrument employed.) 



Supposing that with our present instruments no star 

 below the 10th magnitude can escape us, why should we 

 not trust, our star-gauges up to that magnitude ? And 

 why should we not use the general luminosity of the 

 sky as an indication of the distribution of still fainter 

 stars ? 



I am not writing in favour of either a finite or an 

 infinite Univei-se. I only desire to call the attention 

 of astronomers to one of the unsolved problems which 

 the science presents ; and I am surprised to find so 

 many writers both in your columns and elsewhere dealing 

 with it on popular or metaphysical grounds rather than 

 as a scientific problem. 



W. H. S. MoN-CK. 



P.S. — In my last letter " a Centauri " was printed 

 " and Centauri." The reader will no doubt have seen 

 the mistake. 



[I must express my full agi-eement with the con- 

 cluding words of Mr. Monck's letter. The cjuestion of 

 the shape and extent of the general .sidereal universe as 

 it presents itself to us seems to me an interesting and 

 important one, and any mode of enquiry which woi Id 

 enable us for instance to form an estimate of the mean 

 distance of the Galaxy and of its mean depth should I 

 think be welcomed and carefully examined. But the 

 general question ''Is the Stellar Universe finite?'' be- 

 comes at once not a physical but a metaphysical enquiry, 

 and hence leaves the domain of astronomy, and except as 

 a purely mental exercise I see no value in it. How ea^ly 

 even the keenest and most trained minds may go astray 

 on the subject may be learned from Prof. Newcomb s 

 paper in the March number of the " Windsor Magazine.' 

 He writes " It can be shown mathematically that an 

 infinitely extended system of stars would fill the heavens 

 with a blaze of light like that of the noonday sun." 

 There is a tacit assumption here that the stars are on the 

 average uniformly distributed in space, an assumption 



which for nearly a coulury astronomei-s have known to 

 be untrue. 



I must ask, therefore, that correspondeiKts in future 

 will leave the general and metaphysical (jucstion entirely 

 alone, and confine themselves to the question of the 

 actual distribution of the known stars. 



[E. W.\LTi;U M.WNDKK.J 



■ » I — 

 WIRELESS-TELEGHAl'Il REt'KlVEIl. 



TO THE EDITORS OF KNOWLEDGK. 



Sius, — One evening la.st summer I was using the 

 receiver in the ordinarv wav in connection with a Morse 

 jirinting maihine ; it was a dull evening with a good deal 

 of thunder about ; and I noticed that a dot was printed 

 at every flash of lightning. Of course that would be ex- 

 pected, since the receiver was not protected in any way, 

 but when I joined up a small galvanometer in place of 

 the Morse machine, I found greatly to my surprise that 

 the needle of the galvanometer was affected by the 

 lightning through the coherer, an instant before the flash 

 was visible to me. I noticed it several times. The 

 only explanation I can think of is that the electric 

 discharge caused by the lightning has a quicker effect 

 upon the coherer than upon the human brain or nerves. 



XoRM.\x Robinson. 



[The really important conclusion to which your 

 correspondent s observations seem to point is this : -- 

 The galvanometer used was sensitive to something which 

 occurred immediately before the lightning flash was 

 made manifest, as regards which, it seems clear that the 

 " recorder " took no note of it. Two questions ai'e at 

 once suggested : What was this something, and, was 

 the galvanometer in no way iiffected by the imme- 

 diately succeeding, and expected, effect which caused 

 the Moi-se to "dot"? Stating the second question in 

 another way, " Did the needle give but one kick?" 



Again, as regards the producer of the effect alluded 

 to, apparently it was Hertzian, Electro-magnetic, or 

 Electro-static. Possibly it was forces of these three 

 natures acting together, or any two of them in con- 

 junction — if not a single one. Unfortunately Mr. 

 Robinson gives us no details as to the windings (and 

 self induction co-eflicients) of the instruments which he 

 used — and interchanged. However, the subject is one 

 of great interest, and it seems that no one has hitherto 

 wandered into the path indicated. — How.\rd B. Little.] 



A CLOUD OF DRIED BEECH LEAVES. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — The following may be interesting, not only as 

 an unusual occurrence, but as bearing on the question 

 of aerial tran.sportation of seeds, etc. 



At about four o clock on the afternoon of Sunday 

 last (April 1st), my attention was arrested by the fall 

 of numbers of dried beech leaves. On looking up I 

 found that the leaves were passing in large numbers 

 from east to west, and as high as the limit of vision. 

 Many appeared to be mere specks, whose height r.nd 

 motion promised them a journey of some miles at least. 

 The shower continued for perhaps twenty minutes. The 

 fall was noticed by many persons here, who were unable 

 to account for it, as there arc no beech trees within two 

 miles at nearest. Probably the leaves had been raised 

 by a whirlwind, and at a very considerable distance 

 east of this neighbourhood. 



A friend, who was some three miles east of my station. 

 witnessed the phenomenon, and states that by the aid 

 of a field-glass he could see leaves still higher than tnosc 



