ontal Magnetic Force. 



i_184:j-'46. I o o I +0-5 i +0-7 | +0-9 I +0 4 | +o-3l +o-5! +0 6! -4-o il -o-el -o-ej -o a 

 Lj8f3J^5. I +0-7 1+01+04 +o-^ 4-0-3 -o-4l -o-e! -o-tI -i3' -.oI -o-sI -0-9 



Before proceeding to the analysis of the final result of table 

 I^'o. 8, the separate results were combined into summer and win- 

 ter groups, the first comprising the months from April to Sep- 

 tember, the second group the winter months from October to 

 March. 



The results are exhibited in the annexed diagram A. The 

 number of observations, about eleven thousand lor each group, 

 is evidently too small to eliminate the greater irregularities. 



If there is any marked difference in the lunar diurnal variation 

 in the summer and winter season, the summer range is slightly 

 greater than the winter range. As to the epoch there is no 

 doubt that in winter the lunar maxima and minima are earlier 

 ^liau in summer. It is a remarkable fact that the same feature 

 shows in the lunar effect on the declination, namely, a greater 

 arnphtude in summer and an earlier occurrence of the maxima 

 and minima in winter. The amount of the shifting of the two 

 curves seems to be nearly the same. 



From tiie ten years series of observations at Prague (1840- 49), 

 Mr. Karl Kreil found a larger lunar effect in summer months 

 than in winter 



Recurring to the final values of the lunar diurnal variation of 

 the horizontal force, as given in table Ko. 8, they can be repre- 

 sented by the usual Besselian form of periodic functions. 



The curve is double crested and is exhibited together with 

 the observed values in the annexed diagram. It presents two 

 maxima and tw^o minima. (See diagram B.) 



The lunar effect on the declination we have found also to pre- 

 sent two maxima and two minima as stated in Part III. of the 

 discussion. ^ , , 



An examination of the diagram just referred to, shows;— 

 Pnncipal maximum 2^ 52°' after upper culm.; -f- 0-78 scale divisions. 

 Secondary " " 1 7 " lower ^'^' ', -^Oo\ 



Secondarv " ' 8 19 " "Pper " ; -^-^^ 



