156 



Absteacts foe the Total Intensity. 



aE, 



TABLE XXIX. — Monthly Mean Values of ~^> the Differences of Total Magnetic Intensity, in parts of tho 



whole force, for the Observation Hours of 1842 ; deduced fi'om Tables X. and XVIII., the value of 



aR 



R 



December 20'^ being taken as 



Zero. 























Mean of the 



Range 1 



Month. 



SOi. 



23^. 



2^. 



5". 



Four Hours. 



For each 



For each Two 















Month. 



Months. 



January 



000208 



000214 



000220 



0-00227 



000217 



000019 



0-00018 



February 



0-00191 



0-00196 



0-00200 



0-00208 



0-00199 



0-00017 

















0-00024 



March 



000140 



0-00146 



000147 



000172 



000151 



0-00032 



000039 



April 



000131 



0-00121 



000130 



0-00168 



000137 



0-00047 

















000058 



May 



0-00132 



0-00110 



0-00121 



000180 



0-00136 



0-00070 



000053 



June 



000107 



0-00099 



0-00108 



000136 



000112 



0-00037 

















0-00058 



July 



0-00094 



000046 



0-00055 



0-00125 



0-00080 



0-00079 



000056 



August 



0-00067 



0-00052 



0-00064 



000086 



000067 



000034 



0-00040 



September 



000049 



000050 



0-00076 



000095 



0-00067 



000046 



0-00040 



October 



000032 



0-00035 



0-00045 



0-00067 



0-00045 



0-00035 



000034 



November 



0-00016 



0-00028 



00044 



0-00049 



0-00034 



000033 



000026 



December 



000000 



000005 



000016 



000019 



000010 



0-00019 





This Table has been computed from the formula = sin^ 6 ~— — ^- cos^ d . 



II Y X 



aE. 

 TABLE XXX. — Mean Values of for Three Months, for the Summer and Winter Months, and for the 







Year 1842. 









Period. 



20t'. 



231'. 



2^. 



5i>. 



Range. 



Mean of the 

 Four Hours. 



1842. 

 Jan., Feb., March 



0-00180 



000185 



000189 



0-00202 



0-00022 



000189 



April, May, June 



0-00123 



0-00110 



000120 



0-00161 



000051 



0-00128 



July, Aug., Sept. 



000070 



0-00049 



000065 



0-00102 



000053 



0-00071 



Oct., Nov., Dec. 



0-00016 



0-00023 



0-00035 



0-00045 



0-00029 



0-00030 



Jan., Feb., March, \ 

 Oct., Nov., Dec. J 



0-0G098 



0-00104 



000112 



0-00123 



0-00025 



0-00109 



April, May, June, \ 

 July, Aug., Sept. J 



0-00096 



0-00080 



0-00092 



000132 



0.00052 



0-00100 



The Year 



0-00097 



0-00092 



0-00102 



0-00128 



0-00036 



0-00105 



A maximum of total intensity probably occurs in the winter months before 23'', and a minimum between 

 23'' and 2". 



The maximum seems to occur earlier in the summer months, and the minimum nearer 23*^ than 2*^. 



The total intensity decreases from quarter to quarter, the rapidity of decrease diminishing rather regularly. 



I 



