126 



NATURE 



[May 30. 1878 



the petals of flowers. Let us take the white lily. If the 

 petal of the flower had been merely a sheet of thin glass 

 you would not hare seen that white colour. There 

 would have been a little light reflected from the first 

 surface and the back surface, but the petal is really 

 composed of a vast assemblage of little cells, at each 

 of which partial reflection takes place, so that it re- 

 sembles some finely-powdered glass, which would form 

 a white powder, because each little surface is capable of 

 reflecting the light, although a single sheet of glass would 

 not be white. The petal of the white lily is just in the 

 condition of the powder. It is full of little cells, full, 

 optically speaking, of irregularities, from each of which a 

 portion of light is reflected, so that, all kinds being reflected 

 alike, and there being nothing in the white lily to cause 

 preferential selection of one over the other — nothing to 

 sift the light, as it were — you get a considerable quantity 

 of light reflected back to the eye, but it is white. What 

 is the difference between that and the red poppy ? The 

 red poppy is, as it were, a white lily infused with a 

 red fluid ; there is light continually reflected backwards 

 and forwards, just as before, at the surface of the cells ; 

 but that light, in going and coming, passes through the 

 coloured juice of the plant. It is the same thing with a 

 green leaf. The structure is irregular, optically consi- 

 dered ; there are constantly reflections, backwards and 

 forwards, of light, which penetrates a little depth and is 

 reflected, and has to pass through a certain stratum of 

 this colouring matter, to which the name chlorophyll has 

 been given, but which is really a mixture. That is what 

 takes place generally as regards the coloration of bodies ; 

 it is a phenomenon not of reflection, not of selection of 

 one kind of light for more copious reflection than another, 

 but of absorption, or the swallowing up of certain kinds 

 of light. Reflection comes in in order to enable us to see 

 the light which otherwise would not enter the eye at all, 

 but would go off in another direction." 



J. Norman Lockyer 



COSMIC METEOROLOGY 



SEVERAL articles have appeared at different times 

 under the title of "La M^t^orologie Cosmique," 

 from the pen of M. Faye : the last and most complete 

 forms an exceedingly interesting " Notice Scientifique," 

 appended to the Aimuaire of the Bureau des Longitudes 

 for 1878. In this memoir, written with the usual clear- 

 ness and talent of the distinguished French astronomer, 

 a number of results connected with real or supposed 

 solar, lunar, and planetary actions on our earth are ex- 

 amined and criticised. As M. Faye has omitted several 

 facts of considerable importance in his " Notice," and 

 has misunderstood others, a reconsideration of some of 

 the questions he has studied, with the additional light to 

 be obtained from the facts alluded to, may not be without 

 interest and use. 



M. Faye's thesis is giren in the first words of his 

 article " Meteorological phenomena have their origin in 

 solar heat." It is added, "This is now no longer suffi- 

 cient. Cosmic influences are introduced, those of the 

 planets, of the spots and rotation of the sun, of shooting- 

 stars, the moon, and besides these, magnetic and electric 

 actions are supposed to intervene incessantly between the 

 bodies of the solar system." I shall refer to some of 

 the most important questions under their different heads. 



The Moon's Influence in producing Atmospheric Varia- 

 tions. — The popular beliefs in the moon's influence on 

 the weather are first disposed of; they are conclusions 

 from unrecorded observations where the coincidences are 

 remembered and the oppositions are forgotten ; and they 

 are opposed to strict deductions when all the facts are 

 ■employed. 



Agreeing, as all men of science do, with this decision, 

 the question remains. Whether the moon may not have 



some slight effect in producing meteorological variations ? 

 She reflects, absorbs, and radiates the solar heat ; may 

 this heat, in accordance with the thesis, not produce some 

 effect on our atmosphere ? 



Sir John Herschel had observed the tendency to' disap- 

 pearance of clouds under the full moon ; this he con- 

 sidered a fact which might be explained by the absorption 

 of the radiated lunar heat in the upper strata of our 

 atmosphere. He cited Humboldt' s statement as to the 

 fact being well known to pilots and seamen of Spanish 

 America. I may add the testimony of Barnardin de St, 

 Pierre, who, in his "Voyage kl'Ile de Reunion," says : 

 " I remarked constantly that the rising of the moon 

 dissipated the clouds in a marked way. Two hours after 

 rising, the sky is perfectly clear " (" Avril, 1768 "). Her- 

 schel also cited in favour of his "meteorological fact," 

 a result supported by the authority of Arago, that rather 

 more rain falls near new than near full moon. 



Arago' s conclusion that the phenomenon was "incon- 

 testable of a connection existing between the number of 

 rainy days and the phases of the moon " was founded on 

 the observations of Schiibler, of Bouvard and of Eisen- 

 lohr, three series which, on the whole, confirmed each 

 other. Schiibler also, as Arago showed, had found 

 that the quantity of rain which fell was greater near new 

 than near full moon. These results, accepted by Arago, 

 have not been noticed by M. Faye when he cites Herschel 

 only, as one of those " men of science who interest them- 

 selves in popular prejudices, take bravely their defence in 

 hand and exert themselves to furnish not facts but argu- 

 ments in their favour." It seems, indeed, to have been 

 forgotten that Herschel' s argument was given to explain 

 what he considered a meteorological fact. 



M. Faye founds his argument wholly on the conclu- 

 sions of M. Schiaparelli from a weather register kept at 

 Vigevano by Dr. Serafini during thirty-eight years (1827- 

 1864).^ The Italian physician entered the weather as 

 clear, cloudy or mixed {misti), or rainy from morning 

 to evening. M. Schiaparelli finds from this register 

 that the sky was clearest in the first quarter of the moon. 

 It has not been remarked that if the moon' s heat has any 

 effect in dissipating clouds, as Herschel and others 

 believed, this must be seen best when the moon is near 

 full, that is to say, during the night hours, for which Dr. 

 Serafini' s register has nothing to say. In confirmation 

 of the conclusion that the moon does not dissipate the 

 clouds, another result from the Vigevano weather jegister 

 is cited, namely, that the greatest number of rainy days 

 happens near full moon. This result is opposed to that 

 derived from the observations of Schiibler, Bouvard, and 

 Eisenlohr. 



The value to be given to observations of the number of 

 rainy days must evidently depend on whether the observa- 

 tions include the rainy nights ; and an investigation on this 

 question, to have any considerable weight, should depend 

 rather on the measured rainfall than on the term " rainy 

 day," for which no distinct definition is given. 



The great objection to M. Faye's conclusions, as far as 

 the facts go, is to be found in their entire dependence on 

 tha Vigevano weather register {da mane a sera). No 

 notice is taken of other observations and results showing 

 a lunar action on our atmosphere, such as those already 

 mentioned, which Arago considered incontestable, those 

 of Madler and Kreil, and the more recent investiga- 

 tions of Mr. Park Harrison and Prof. Balfour Stewart. 

 All of these, and many others, must be carefully considered 

 before we can accept the conclusion that the moon has 

 no influence on our atmosphere. The subject is, how- 

 ever, too large to be entered into here at present, and 

 it will be possible to study it better after other conclusions 

 of the learned French Academician have been examined. 



There is, however, a part of the argument, whatever 

 the results obtained may say, which merits particular 



' Memorie del R. Istituto Lombardo, L. lo. 



