ATMOSPHERIC MAGNETISM— SINGAPORE. 
115 
same hours, up to 19 o’clock, is in striking contrast ; and I have attributed the differ- 
ence to the effect of a cold region coming on from the east during the former months 
(3061.), which is absent in the latter months. In reference to this point, we have 
again to consider that the warm region is on the north of the equator (3063.), and 
that as the sun moves north and south it also will move with it, but still keeping north 
of it. Hence the two cold regions, which come up to the meridian in higher latitudes 
(3006.) before the sun, will not be in the same relation to Singapore, for the one on 
the south will be nearer to it than the one on the north, or at all events more powerful. 
So when the sun is near and at the southern tropic, the warm region probably passes 
(wer Singapore, at which time, therefore, whilst it is the nearest, the most powerful 
and most direct in position, the cold regions will be least in force at the station, and 
also least favourably disposed by position. But when the sun is at the northern 
tropic, then the power of the warm region is diminished, both by distance and direc- 
tion, and the southern cold region grows up into importance by increased strength 
and closer vicinity, and so produces the eastening before 19’'. 
3066. A striking difference in the direction of the night curves, from 5^ to 14’', at 
St. Helena and Singapore may be observed. At the former place the needle end 
tends first east and then west, whilst at the latter it moves first west and then east. 
The difference is, I believe, due to the appearance of night cold action at St. Helena 
to a greater extent than at Singapore. Singapore shows that action in June, July 
and August, as just described (3065.), but only in a weak degree and at a late hour. 
At St. Helena, which is in latitude 16° S., the cold effect should, for the reasons given 
above (3065.), appear in more power, and hence the eastening at 6’' and after; and 
that this is the cause is indicated also in a degree by the tables of temperature ; for 
whilst at Singapore the difference between the maximum and minimum in the twenty- 
four hours is only from 3° to 4°, at St. Helena it is from 4°*5 to 7°, and four-fifths or 
even five-sixths of this depression occurs by 9 o’clock : so that four or five hours 
before that, there was in the east a cold region coming up and producing the 
eastening effect recorded in the curves. 
3067. The inclination variation at Singapore is beautifully simple, and such as 
might be expected from the hypothesis ; the sun or warm region, when passing the 
meridian, always being over the lines to depress them. It is alike in all the months, 
being greatest at night-time and least at midday ; it is nearly the same from 8’' to 18’'; 
then as the sun comes up it decreases quickly until 23’' or 24’', after which, as the sun 
passes away, it increases nearly as quickly until 7^ or 8^ The amount of variation is 
greatest when the sun is over or to the south of Singapore. It is least in June and 
July, when he is near the northern tropic. In December and January, when he is near 
the southern tropic, it is considerably more than in June and July, which again seems 
to show that the warm region is chiefly north of the sun (3063.). 
3068. The total force variation is simple, being a maximum from 9’' to 12’', and a 
minimum at 22’' or 23’', near noon. The greatest variation is in April and October, 
Q 2 
