482 THE POPULAR SCIENCE MONTHLY. 



which we receive most of our storms ; so that the apparition of the 

 old moou in the arms of the new, virtually means that there are vast 

 cloud-banks over the North Atlantic Ocean which, in all probability, 

 are drifting up to us, and will, before long, bring us " dirty " weather. 

 I am not disposed to go so far as Mr. John Aitken, who, in a paper re- 

 cently read before the Royal Society of Edinburgh, suggested the use 

 of the moon's dark limb as an " outlying signal station," but it is sat- 

 isfactory to know that this venerable prognostic has a soimd physical 

 basis, and is as worthy of respect as ever it was. The other explana- 

 tion to which I referred is the greater " visibility " of the air which 

 generally precedes rough or unsettled weather, this clearness allowing 

 the ghostly disk of the old moon to loom forth in a way it could not 

 do through a misty atmosphere. Though, doubtless, a part explana- 

 tion of the phenomenon, it is not a whole one, and must be taken along 

 with the other. 



The halo is an old sign of bad weather ; 



" When round the moon there is a brugh, 

 The weather will be cold and rough." 



Of sixty-one lunar halos observed in the neighborhood of London, 

 thirty-four were followed by rain within twenty-four hours, nineteen 

 by rain within four days, and only eight by no rain at all. The cause 

 of halos is the formation of an extremely attenuated form of cloud 

 which floats in the van of all cyclonic disturbances. Messrs. Aber- 

 cromby and Marriott, who made a detailed comparison between a 

 number of popular weather prognostics and the actual distribution of 

 weather as disclosed by synoptic charts, found the lunar halo to be a 

 true sign of the approach of a " cyclone " or area of depression, just ay 

 a clear moon indicates the presence of an anti-cyclone, or area of high 

 pressure, with the likelihood of cold or frost. Similarly, a pale or 

 watery moon marks the advent of a disturbance, while the blunting of 

 the cusps is due to the same cause, and has the same significance. The 

 variation of this last prognostic, which makes a sullied lower horn the 

 sign of foul weather before the full, and a sullied upper horn the sign 

 of foul weather about the wane, is purely fanciful. 



Just one word about that enticing object of research — as fascinating 

 in its way as perpetual motion or the exact value of tt — the lunar circle. 



Dr. E. B. Tylor, says : " The notion that the weather changes 

 with the moon's quarterings is still held with great vigor in England. 

 That educated people to whom exact weather records are accessible 

 should still find satisfaction in the fanciful lunar rule, is an interesting 

 case of intellectual survival." I am willing to be with the foremost 

 in combating such absurdities as "Herschel's AVeather Table," and all 

 theories which would assign to the lunar phases an immediate control 

 of our weather ; but it so happens that the notion Dr. Tylor con- 

 demns is one for which there may be some foundation. A moon's 

 quarter is roughly equivalent to a week, and Mr. Carpmael, the Di- 



