A. D. Bache on Declinometer Observations. 41 
mum was found by a special formula. It took place in August, 
1843, and as a resulting epoch from this and the previous deter- 
mination, June, 1843 may be adopted. This is graphically rep- 
resented on diagram C. : 
The following table gives the ratios of the aggregate amount 
of disturbances in each month of the year: 
Total Ww | E. | Total Ww. E. } 
January, 72 Fer 0°33 PJuly, 0°87 0°46 1°29 
February, 0'54m5| 059 046 jJAugust, 1°61 95 1:28 
. 06 ( 66 September, 1°56 0°99 2°12 
April, 0°94M.| 1:04 | 0°84 |October, 2°06M,| 1°67 | 2-46 
; 05 0°52 0°56 [{November, | 1°06 )9 1°02 
June, 0°42m,| 037 0:47  |December, 10 138 0°6 
August and October) and April; and minima in June and Jan- 
uary (same as at Toronto). 
e arrangement according to the hours of the day gives the 
following ratios, to which is added, in the last column, the diur- 
nal disturbance variation obtained by dividing the excess of ag- 
gregate westerly over easterly values by the total number of 
ys of observation. 
Philadeiphia ee Disturbance, } 
mean time. w E. Both com- yariation in are. 
: bined. 
oo 
0 (194) 0:83 1-24 1-0 —016 
2 1:16 1°10 118° -00 
.= 1:16 0-92 1:04 +005 
. es 0°67 1:06 +0°24 
. 1°39 0:67 1:02 +0: 
ee 1-22 OTT 0-99 +013 
Noon “ 1-03 0-68 083 +011 
ee 098 063 080m +010 
14 of 0:99 0-72 0°85 +007 
a." 084 ., eos 0°84 —0°02 
20 « 038m 188M 1:15 —053 
22 (194) 1:88 125M —0°47 
number, we find, irrespective of the direction of the deflec- 
reserved. ‘The maximum is earlier 
tions, the 2 P. M. minimum 
and oc¢ursat 10 p.m. (At Toronto these hours are respectively 
1P.M.and9 P.M.) At Philadelphia as well as at Toronto the 
860. 
SECOND SERIES, Vor. XXIX, No. 85.—JAN., | 
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