VARIATION OF MOONS MOTION. 



shall find a like variation. The following are the dates of twelve 

 successive lunar months in 1855, and their lengths severally are 

 given in the second column : 



1855. 



NEW MOONS. 



Jan. 13 

 Feb. 16 . 

 March 18 

 April 16 

 May 16 

 June 14 . 

 July 14 

 Aug. 12 

 Sept. 11 

 Oct. 11 . 

 Nov. 9 

 Dec. 9 . 



INTERVALS. 



D. H. II. S. 



29 10 10 6 



29 9 57 42 



29 10 19 18 



29 11 8 48 



29 12 15 36 



29 13 32 6 



29 14 51 24 



29 15 59 18 



29 16 32 



29 16 7 18 



29 14 46 48 



Thus it appears that these eleven lunar months vary in length 

 from 29 d 9 h 57 m 42' to 29 d 16 h 32 m 0% and if the comparison were 

 carried further, a still greater variation would be found. 



89. The causes of this great and apparently irregular variation 

 in the motion of the moon are very numerous and complicated, as 

 may be imagined when it is stated, that in order to deduce the 

 moon's true place in the heavens at any proposed time, from its 

 place as resulting from its mean or average motion, it is necessary 

 to apply from thirty to forty corrections, each of which represents 

 the effect of some disturbing force, the principal of which, how- 

 ever, are traceable to the varying action of the sun upon the 

 moon. 



90. It appears from the preceding table, that the day of new 

 moon may fall indifferently upon any day of the calendar month. 

 In common popular language, and more especially upon occasions 

 on which certain influences are imputed (however erroneously) to 

 the moon, that luminary is associated with the month, so that we 

 hear of this and that effect of the "May moon," or the " March 

 moon," and so on. Now, as neither the beginning nor the end of 

 the age of the moon, nor even its length, has any necessary 

 correspondence with the beginning or the end or the length of the 

 month, it may be asked, by what condition the " May moon " is 

 connected with May, or the " March moon " with March. 



It might be imagined that the moon would take its name from 

 the month in which it passes the greater part of its life. Such, 

 nevertheless, is not the case. According to the most generally 

 adopted custom, the moon takes its name from the month in which 

 its age terminates. Thus, the May moon is that moon which ends 



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