388 



THE MOON AND THE WEATHER. 



There are here no traces of correspondence in the extremes of temperature, 

 or the quantities of rain. It is manifest that any season taker; at hazard would 

 not present greater discordances than are found in the above table. 



The variation of the moon's distance from the earth (to which we have more 

 than once adverted) is occasioned by the fact that her path round the earth is 

 not circular, but oval the position of the earth being nearer to the one end 

 than the other. As the moon, therefore, approaches the furthermost extremity 

 of her oval orbit, her distance from the earth continually increases until, arri- 

 ving at that point, it becomes greatest ; as she moves from that extremity of the 

 orbit to the other end of the oval, her distance continually diminishes until ar- 

 riving at the other end, it becomes least. These variations of distance are 

 produced every revolution of the moon round the earth. Now, owing to a* 

 certain change of position, to which the moon's orbit is subject, the points which 

 mark her greatest and least distances are subject to a slow, gradual, and regu- 

 lar change. ; so that the points in the heavens at which she reaches her great- 

 est and least distances are different every revolution. After the lapse, how- 

 ever, of eight years and ten months, these points having traversed the whole 

 circumference of the heavens, resume their former position very nearly ; so 

 that the actual times at which the moon is observed at the same distances from 

 the earth, and also at the same points in the heavens, recur in a cycle, the 

 length of which is about eight years and ten months. 



So far, therefore, as the vicissitudes of the weather can be supposed to be 

 influenced by this cause, their period should be such that, after the lapse of 

 nine years, the corresponding states of the weather would be, as it were, two 

 mo;iths in advance : thus the effect produced in December, 1800, would again 

 be produced in October, 1809, in August, 1818, and so on. 



If the purpose be to determine the cycle in which the lunar influence, so far 

 as it depends on distance, would produce the same effects upon the same days 

 of the year, the duration of the cycle would be six times eight years and ten 

 months : for in six successive intervals of that period, there are exactly fifty- 

 three years ; but any less number of periods of eight years and ten months do 

 not make a complete number of years. Therefore after a cycle of fifty-three 

 years, the moon being on the same day of each successive year at the same 

 distance from the earth, her influence, so far asdepends on distances, will be 

 ti\3 same, and will produce the same effect upon the weather. 



Now we cannot better illustrate the loose and inaccurate manner in which sci- 

 entific principles are applied by some meteorologists than by stating that this cy- 

 cle of eight years and ten months has formed the theoretical grounds for a re- 

 puted meteorological period of nine years. It has been maintained that, 

 through every successive interval of nine years, the changes of weather have 

 a general correspondence : thus, if the state of the weather throughout the 

 year 1800 be examined, it has been said to correspond with the weather 

 throughout the years 1809, and 1818, &c. 



That the changes in the positions of the points of the moon's greatest and 

 least distance are insufficient in theory to account for such meteorological cy- 

 cle as we have explained. But let us see how the fact stands. 



Toaldo, whose meteorological researches we have adverted to, has stated, 

 that at Padua, by resolving a long interval of time into successive periods of 

 nine years, the quantities of rain collected in each of these periods were equal, 

 but he adds this equality would disappear if the whole interval were resolved 

 into groups of eight years, or into successive intervals of any other number of 

 years. M. Arago, taking the Italian meteorologist at his word, and accepting 

 without question, his own tables and data, has given the following estimate of 

 the quantity of rain which had fallen in successive intervals of nine years : 



