WEATHER PROGNOSTICS. 



The same causes, also, which at new and full moon produce 

 spring tides, and at the quarters neap tides, would produce spring 

 and neap atmospheric tides at the same epochs. At new and 

 full moon, therefore, the air ought to be higher, daily, at noon 

 and midnight than at any other times during the month ; and, on 

 the other hand, at quarters it ought to be lower. 



If, then, the barometer be observed twice daily, viz., at the 

 times of the moon's transit over the meridian, above and below 

 the horizon, it ought (so far as it will be affected by the sun 

 and moon) to be the highest at new and full moon, and lowest at 

 the quarters. Now as the rise of the barometer generally indi- 

 cates fair weather, and its fall foul weather, the conclusion to 

 which this would lead would be, that the epochs of new and full 

 moon should be generally fair, while at the quarters bad weather 

 would generally prevail. 



This, however, is not the popular opinion. The traditional 

 maxim is that a change may be looked for at new and full 

 moon ; that is, if the weather be previously fair, it will become 

 foul ; if previously foul, fair. 



M. Arago submitted to rigorous investigations a series of 

 barometric observations made in relation to the lunar phases at 

 the Paris Observatory, and continued for twelve years, and found 

 that the effect of the lunar attraction on the barometer at the 

 epochs of the high and low atmospheric tides could not have 

 exceeded the l-600th of an inch, a quantity such as could 

 produce no conceivable effect upon the weather. 



It is evident, then, that if the moon have any influence on our 

 atmosphere, it cannot proceed from any cause analogous to that 

 which produces the tides of the ocean. 



But it may be said that although the moon may not affect the 

 atmosphere by her gravitation, yet she may influence it by her 

 light, or by electrical or magnetical emanations, or, in fine, by 

 some occult physical causes not yet discovered by astronomers. 

 This is an objection that, from its vagueness and indenniteness, 

 is difficult to be rebutted by any means which theory can 

 furnish. It is known that the light of the moon concentrated 

 in a point by the most powerful burning lenses, is incapable of 

 producing the slightest sensible effect on the most susceptible 

 thermometer. Neither is it found to produce any effects of an 

 electrical or magnetical kind. It may be assumed generally, that 

 the effects commonly imputed to the moon, in producing change 

 of weather at her principal phases, are so contradictory, that it 

 is impossible to imagine any physical causes which could account 

 for them. If the new and full moon and the quarters are 

 attended by changes of the weather, the cause producing this effect, 

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