142 



Abstracts for the Horizontal Force. 



TABLE X. — continued. 



Month. 



20'-. 



23i>. 



SK 



5^. 



Mean of the 

 Pour Hours. 



Range from the 

 Four Hours. 



1842. 



Sc. Div. 



Sc. Div. 



Sc. Div. 



So. Div. 



Sc. Div. 



Sc. Div. 



July 



512-39 



507-18 



521-85 



529-82 



517-81 



22-64 



August 



512-91 



507-43 



523-34 



528-91 



518-15 



21-48 



September 



518-03 



511-58 



524-85 



527-77 



520-56 



16-19 



October 



525-19 



519-88 



528-01 



529-39 



525-62 



9-51 



November 



527-27 



525-24 



530-71 



531-40 



528-65 



6-16 



December 



532-36 



530-15 



535-20 



534-90 



533-15 



5-05 



In Tables VIII. and IX. the mean of the four observations has been given as an approximate mean for each 

 month ; the last column contains the range deduced from these four observations, and is probably not far from the 

 true diurnal range. 



In all the months, with the exceptions of January and December 1842, 23'^ shews the least force of the four 

 hours ; the greatest force is at 5^. In January and December 1842, the greatest force is at 2^ ; in October 1842, 

 and November 1841 and 1842, the force at 2^^ differs little from that at 5*^. The minimum seems therefore to 

 occur throughout the year a little before 23*^ (or before 10'' a. m. Makerstoun mean time) ; the maximum about 5** 

 (or 4:^ p. M. Makerstoun time) in summer, and between 2^ and 5^ (or l'^ and 4^ p. M. Makerstomi time) in winter. 

 In December 1842, the maximum occurs about 2^ p.m. Makerstoun time. The diurnal ranges, as given in the 

 last column, though affected by the shifting of the curve in the summer and winter months, shew markedly a great 

 and regular increase from winter to summer, and decrease from summer to winter. Although the rejection of the 

 days of irregularity have considerably softened the asperities in the Means of Table VIII., the depressions in June 

 and July being considerably removed when compared with May, the depression in April still remains. 



The force on the whole increases from the beginning of the year till the end ; the increase being most rapid 

 after September 1842 ; and it is nearly constant for the summer months. 



The following Table has been deduced from Table X. 



TABLE XL — The Means of the Bifilar Magnetometer Readings minus the least mean, in parts of the whole 

 Horizontal Force, for periods of Three Months, for the Summer and "Winter Months of 1842, and for the 

 Year 1842. 



Period. 



20''. 



23'-. 



2''. 



5^. 



Mean. ■ 



Range. 



1841. 

 July, Aug., Sept. 



Oct., Nov. 



1842. 

 Jan., Feb., March 

 April, May, June 

 July, Aug., Sept. 

 Oct., Nov., Dec. 

 Jan., Feb., March, 1 

 Oct., Nov., Dec. j 

 April, May, June, ) 

 July, Aug., Sept. j 

 The Year 



0-00058 



0-00000 



0-00177 



0-00288 



0-00057 



0-00282 

 0-00339 

 0-00384 

 0-00513 



0-00397 



0-00361 

 0-00379 



0-00288 

 0-00112 



0-00139 

 0-00260 

 0-00251 

 0-00085 



0-00112 



0-00256 

 0-00184 



0-00046 



0-00256 

 0-00279 

 000329 

 0-00502 



0-00379 



0-00304 

 0-00341 



0-00000 



0-00210 

 0-00220 

 000257 

 0-00462 



0-00336 



0-00238 

 0-00287 



0-00071 



0-00312 

 0-00378 

 0-00440 

 000540 



0-00426 



0-00409 

 0-00417 



0-00112 



000349 

 0-00480 

 0-00509 

 0-00547 



0-00448 



0-00494 

 0-00471 



The quarter, July, August, and September, is not comparable with the following period. 

 The Means for 1842 shew a regular increase of force in the first three quarters ; in the last the force increases 

 with more rapidity. 



