0/ >^ 



NATURE 



[August 15, 1895 



shield of astronomy, profess to have framed infallible rules for i 

 the weather as judgoi from the ever-var)ing relative positions 

 i)f the sun, moon, and planets. They attack us systematically 

 antl persistently, api:)ealing to analogy, to reason, and to common 

 sense. But it is sometimes necessar)' to be on our guard, even 

 against common sense, in considering jiroblems to which un- 

 common sense has for centuries been devoted without avail. 

 The well-known action of the sun and moon upon the ocean 

 tides is generally the starting ix>inl of these theorists, and it is 

 soon shown to common sense that when the earth is nearer the 

 sun, or the moon is nearer to the earth (it being remembered that 

 they move in elliptic orbits), or when both sun and moon are, as 

 it were, pulling together, as at new moon, there ought to be a 

 tide of atmosphere caused by their influence similar to the tides 

 of the ocean, which such agencies undoubtedly produce. But 

 we find that whatever .so-calle<l reason, analogy, and common 

 sense may seem to dictate, the facts will not follow in the (xith 

 marked out for them ; and the atmospheric tides refuse to ebb 

 and flow, except in a most infinitesimal degree, quite dispropor- 

 tioncd to their supposed moving forces. The theorists must trj' 

 again, and they do so by jwinting out that the moon and earth 

 move in planes which are inclined to each other at an angle, and 

 that at some limes of the year the attraction of the sun and moon 

 are acting in somewhat widely diverging lines, whilst at others 

 they are pulling more nearly in the same jilane. Here is, they 

 say, a clear case. .\t times, when the angle is gre.itest, there 

 should at any rale be worse weather caused by the conflicting 

 forces. When the moon is said to be " on her back," or, in other 

 words, when the line of the shadow boundary of the half-moon 

 or crescent is much inclined to the earth's axis, then is the time, 

 say they, for tempests and commotions to come. But again the 

 spirits from the "vasty deep" do not come when called, and we 

 have to invent other causes for our earthly disturbances. 



It may Ije- safely saiil that a new moon theory as to the weather 

 comes out at least once a year, and it has been attempted to 

 connect the honoured name of .Sir William lierschel with a table 

 which profes.sed to show the dependence of weather changes on 

 those of the moon. 



By the kindness of Mr. Symons I am able to show you on 

 the screen a much magnified representation of this production, 

 now very scarce, and which has the name of lierschel in Ltrge 

 capitals, no doubt as a sort of ballast to give it weight and 

 steadiness, though it does not definitely state that lierschel had 

 anything to do with it. Herschel's ow n letter on the subject 

 runs as follows : — 



J^ 



1 l%,<r**^ t^ /tC^ 



y- 



'/L, /c^ 



/T-<*L^^^ <^ ^^a-tC'"^*-^-' /4»'-'' ,Wt.<>V isi^^« 











So that .my Itllow ..f ihisScjcicly who .sees one of these diagrams 

 in the future will kn><w that it is a fraud. 



Ofroiii ' ,f j.v^.,y one to check the pre- 



dictions 1 I with respect to the changes 



of the W' 1 K I i!ie change of the ni'Kii; but 



X 



9U 



many eminent men have occupied themselves with the subject,, 

 and the result is that no corres]X)ndence between the two classes 

 of phenomena has been established. 



Dr. Horsley examined the weather tables of 1774, as published, 

 by the Koyal Society, and out of 46 changes of w eather in that 

 year only ten occurred on the days of lunar influence, only two 

 of them being at the new moon, and none at all at the full. M. 

 Flarguergues, of \"iviers. found also as the result of twenty years' 

 observations, that the barometer readings taken when the moon, 

 was furthest from the earth averaged 755 millimetres, and when, 

 nearest, 754 millimetres, show ing a difierence of t millimetre or 

 about '04 inch, and this in a direction against the theory, the 

 pressure being greater by that amount when the moon wtts- 

 farthest from the earth. 



\"arious other weather seers have pinned their faith on lunar 

 cycles, and have predicteil that weather changes woulil repeat 

 themselves, as soon as the sun and moon got back into tlie same 

 relative )X)sitions, which they do in nineteen years, with only an 

 error of an hour and a half. Others, such as Mr. ('•. M.ickenzie,. 

 advocated a cycle of 54 years, but it may be summarily staled 

 that all the cycles have broken down, and that, as far as we know, 

 there is no definite period .after w hich the w eather changes repeat 

 themselves. 



(^ther fallacies about the moon are numerous, such as that the 

 full moon clears away the clouds ; that you should only sow 

 beans or cut down trees in the wane of the moon : that it is a 

 b.ad sign if she changes <m a Saturday or Sunday ; that two- 

 full moons in a month will cause a flood ; that to see the old 

 moon in the arms of the new brings on rain, and many others,, 

 of which a catalogue alone wouUl lake up a good deal of space. 

 M. Flannnarion s;iys that " the moon's influence on the weather 

 is negligible. The heat reaching us from the moon wciuld only 

 after! our temperature by 12 millionlhs of a degree : and the 

 atmospheric tides caused by tlie moon would only aftecl the- 

 barometric pressure a few hundredths of an inch — a (|uantily tar 

 less than the changes whicli are always taking place from other 

 causes." On the whole we are disposed to agree wilh the rhyme 

 which thus sums uj) the subject : 



The moon and the weather 

 May change together ; 

 Hul change of the moon 

 Does not change the weather. 



Even the halo round the moon has been discredited, foi Mr. 

 Lowe found that it was as often followed by fine weather as by 

 rain, and Messrs. Marriotl and .Vbercromby found that the lunar 

 halo immediately ))rece<led rain in 34 cases out of 61. 

 We always have a lingering hope that some future 

 meteorologist will disentangle the overlapping influ- 

 ences, and arrive some day at a definite proof that 

 our satellite after all has something to do with our 

 weather. 



Abciul the sun, also, there are many fall.icies, and ever 

 since the discovery that the spots which appear on hls- 

 surface have a i)eriod of greatest and less freijULncy, there 

 have been theorists in shoals who have sotight to i>rove 

 that this (itct rules our weather. It has undoubtedly 

 been found that the frequency of sun-spois and the 

 variations of the magnetic needle are intimately con- 

 nected ; and it is almost equally well established that 

 the aurora appears ami tlisappears in some sort of 

 .sympathy with the sun-spot variali(ms. Hut this, up- 

 to the present, is as far .as we can get in this direction, 

 for our weather seems to have no ilefinile relation Vy 

 these changes. 



The more recent discoveries of prominences visible 

 round the disc of the .sun during an ecli|)se, and of the 

 light clouds only seen in M. Deslandres speitro- photo- 

 graphs, will no doubt call out new weather theories 

 on the subject. .\nd I nnist confess to a wish llial those 

 mysterious flame-like boilies rushing fmni the sun 

 millions of miles into space, will lie found to have 

 some influence im the upper layers of our earlh* 

 atmosphere ; bul I also hope that we nuiy be saved 

 from a theory on the subject muil more facts are 

 before us. 

 Coming down to earlli again, we are met by a long array of 

 fallacies connected with the behaviour of animals ami planls, and 

 which have a .supposed connection with weather iluuiges. tew 

 of these are .s.. well grounded that they may be considered as- 

 proved, and as nothing is .sacred to a meteorologist, our veteran 



NO. 1346, VOL. 52] 



