OF THE EARTH’S MAGNETISM. 521 
September till February 1845, after which it diminished rapidly and continuously 
(with slight inflections) till June 1846, the end of the series. 
TABLE VIII.—Montaiy MEAN VALUES OF HORIZONTAL INTENSITY (minus A 
ee 
10000° 
CONSTANT) AT THE CAPE OF GooD Hope, 1842-46. 1:00= 









Means. 
Monras. 1842, 1843. 1844. 1845. 1846. || —————_-___——— 
182-45-/1843-46. 
January, ‘ : : 29-03] 48:29| 34:04] 84:10] 49-54] 48°87 | 53-99 
February, : : : 29:93 | 46:82) 28:37] 90°26] 40°70), 488-4) 51-54 
March, . : ; : 37°73| 45:97 | 20:35] 88-48 | 32:91] 48:14) 46:93 
209) : : 5 36°95 | 47-48| 19:13] 84:90) 22-11] 47:11} 43-40 





May, ; : ‘ ; 43°85| 49°73 | 22°80) 83°71| 13-77 || 50°02| 42:50 
June, . : ; é 43°43} 54:13} 26:02} 83°38) 11:77 || 51°74) 43°82 
July, : < ; : 39:43] 50°38) 24-27) 78°71] ... 48:20] ... 
August, . : - 42°70) 50°62) 17:97; 74:93)... 46°55 
September, . A A 42°39 | 49:18] 15-66| 67-58| 1841. || 43°70 
October, A 5 , 44-01 | 48°82) 33:17] 64:74| 0°86 || 47°68 
November, . : ; 42°88 | 50°38| 58°06] 62°57} 11:93 | 53-47 
December, . : , 46:04 | 42-26| 77:97| 55:04 | 20-21] 55-33 



19. The movement at the Cape after November 1848, like that at Toronto 
during the same period, is very remarkable; and it is difficult to determine to 
what extent the great increase before February 1845, and decrease after that 
epoch, are real phenomena. The introduction of a new magnet, if the old wires 
were used, would render an apparent decrease of force after its insertion most 
probable. No explanation can be offered by me for the sudden decrease com- 
mencing after February 1845. 
20. Sr Hetena.—tThe series was interrupted in February 1844. The move- 
ments from December 1841 till February 1842 resembles generally those at the 
other places; the mean for March 1843 shows a slight increase from January, 
whereas at all the other places it is a decrease; from June 1843 the force decreased 
till January 1844, when there was an adjustment. From November 1848 till 
September 1844 the movement at St Helena resembles that at the Cape; from 
June 1844 the force diminishes, with slight exceptions, till December 1845 (the 
end of the series in my possession). The exceptions indicate maxima between 
December 1844 and February 1845, and in June and November 1845. 
21. When we compare the movements at St Helena and the Cape, we find the 
following differences. The force increased at St Helena till March 1842, after 
which it began to diminish: first gently; then, after June 1843, more rapidly; it 
then increased till June 1844, diminishing thereafter. At the Cape the force 
increased rapidly till the month of May 1842, two months after the turn at 
St Helena; it then increased slowly till June 1843, during which period the force 
