446 



LIEUT.-GENERAL SABDfE ON THE RESULTS OF THE 



It is obvious on an inspection of this Table that the deflections of the Declination at 

 Kew, both those that are easterly and those that are westerly, attain a greater amplitude 

 in the months April to September than in the months October to March, and that the 

 extremes appear to be reached at a somewhat earlier hour at Kew in the April to Sep- 

 tember than in the October to March portion of the year. The first of these indications 

 is in accordance with the results at Philadelphia ; the second is not so. With respect 

 to the first, viz., the greater amplitudes in the months April to September, if we take 

 the hours 22 to 3 and 10 to 15 as those of the — variation, and the hours 4 to 9 and 

 16 to 21 as those of the + variation for both half years, we have the sums (disre- 

 garding their half-yearly signs) of the semiannual monthly means for April to September 

 2'-50, and for October to March l'-23. And if, retaining the hours 22 to 3, 4 to 9, 

 10 to 15, and 16 to 21 as the most suitable division in the April to September half year, 

 we adopt the division of 23 to 4, 5 to 10, 11 to 16, and 17 to 22 as possibly preferable 

 for the October to March half year, we have the sums (disregarding their signs) of the 

 semiannual monthly means, 2'-50 in April to September and l'-83 in October to March. 

 In both arrangements the deflections are considerably greater in the April to September 

 half year than in the October to March half year. 



The Kew results appear therefore to be confirmatory of the Philadelphia results as 

 to the greater amplitude of the lunar-diurnal deflections in April to September ; but 

 in regard to a slight priority in the hours of occurrence of the maxima and minima in 

 either half year, the inference from the observations at Kew would be, as far as it goes, 

 dissimilar to that deduced by Dr. Bache from the observations at Philadelphia. 



Such being the case, it appeared the more desirable to make a similar examination of 

 the lunar-diurnal variation of the Declination at a station (Hobarton) in the opposite, 

 i. e. in the southern hemisphere, from whence we have nearly eight years of hourly eye- 

 observations, viz. from January 1, 1841 to September 30, 1848. Table VI. exhibits the 

 semiannual and annual means of the lunar-diurnal variation of the Declination at 

 Hobarton arranged as at Kew and Philadelphia. 



Table VI. — Annual and Semiannual Means of the Lunar-diurnal Variation of the 



Declination at Hobarton. 



