Magnetic Declination. 223 



Variations of Westerly Declination with reference to the Relative Positions op the 

 Sun, Moon, and Earth, as indicated by the Moon's Age. 



A glance at the numbers in the first portion. Table II,, shews, with some irregularities, which may be ex- 

 pected where the effects of irregular causes have not been eliminated, the same result as is deduced from the means 

 for the following groups, namely, that there is a maximum, of westerly declination when the Sun and Moon are in 

 opposition, and a minimum when they are in conjunction. 



Means of Groups. 



19 days to 26 days, 8 days including the Third Quarter, mean .... 0-56 



27 3 ... 7 theNewMoon, 0-23 



4 11 ... 8 the First Quarter, 0-67 



12 18 ... 7 the Full Moon, 0-94 



The westerly declination also has its mean value at the quadratures. 



Variations of Westerly Declination with reference to the Moon's Declination. 

 The second portion of Table II. gives the following : — 



Means of Groups. 



4 days to 10 days, 7 days, including the Moon's passage of the Equator southwards, mean 0-78 



11 17 greatest south declination, 1-00 



18 24 passage of the Equator northwards, 0-33 



25 3 greatest north declination, 1*07 



From these, and from the partial means, it appears that a maximum of westerly declination occurs both when 

 the moon has its greatest north and greatest south declination, the maxima being nearly equal, and that minima 

 occur about the time at which the moon crosses the equator, the principal minimum occurring when the moon is 

 moving northwards. 



Variations of Westerly Declination with reference to the Moon's Distance prom 



THE Earth. 



The third portion of Table II. gives the following : — 



Means of Groups. 



Perigee, 3 days before it and 3 days after it, mean ...... 0*50 



8 days about the mean distance, the Moon moving from the Earth, mean . . . 0*69 



Apogee, 3 days before it and 3 days after it, mean ...... 0*20 



8 days about the mean distance, the Moon approaching the Earth, mean . . . 0'72 



As the periods of Apogee and Perigee in 1843 are nearly the same as of the moon's passage of the equator, 

 the results for the mean distance will be similar to those for the greatest north and south declination. It will 

 require two or three year's results to determine to which period the changes are referable. As it is my belief that 

 the apparent variations of the magnetical elements with the moon's distance are really due to variations of declina- 

 tion, I have not in this, or in succeeding cases, pointed out the conclusions to which the means lead. 



