100 
ME. C. V. WALIiEE ON MAGNETIC STOEMS AND EAETH-CUEEENTS. 
1 : 3‘5. Three currents are recorded as having continued for more than one hour; 
sixteen as having continued more than half an hour. The 1-minute currents are most 
in number, namely, eighty, or nearly one-fifth of the whole ; the next in number are 
the 2-minute currents, seventy-five. Then follow the 3-minute and the 4-minute, the 
■|-minute and the 5-minute. 
The division h of the Table shows at a glance the total period of observation on each 
day, the total number of minutes during which N. currents were collected, and those 
during which S. currents were collected, and the sum of the whole. On August 8 the 
S. currents exceeded the N. by 49 min. ; on August 9 the N. exceeded the S. by 1'5 min. ; 
on August 10 the S, exceeded the N. by 28 min. ; August 11, N. exceeded S. by 57 min. ; 
August 12, S. exceeded N. by 24 min. ; September 7, N. exceeded S. by 21-5 min. 
During the whole series the S. currents exceeded the N. by 21 minutes. The dmsion c 
of Table IX. shows the mean duration of the N. and S. currents on each day, and the 
mean of the whole series. On some days the mean duration of the N. currents exceeded 
that of the S. currents ; and on other days the reverse was the case. But taking the 
mean of all the observations and all the days, as given in the last column, the values of 
each are nearly the same. We have 9 ’51 min. as the mean for the N. currents and 
9*42 for the S. 
In Table X. the total number of currents are arranged according to their values in 
degrees ; that is, according to their action on the galvanometer. In division a of the 
Table, the first column contains the galvanometric degrees, in divisions of 5° each, 1° to 
5° being the first in the list, and 81° to 85° being the last. The column under each date 
is subdivided, the N. currents being entered under the first division, and the S. under 
the second. The sums of N. and of S. currents for each value are then given ; and these 
are added to give the total of currents for each value. It will be seen, by referring back 
to Table II., that a deflection of 5° is equal to that produced by three cells of an ordi- 
nary telegraph battery in a circuit of 51J miles. One cell will give about 2°. The 
greatest number of currents are found with a value varying between 15° and 20°; they 
are 91. The next in number, 84, range between 5° and 10°; then follow 56 rangmg 
betw'een 10° and 15°. The proportion of currents which exceed 40° to those which do 
not, is as 59 : 383, or as 1 : 6‘49. The similar proportion of N. currents is 32 : 193, or 
1 : 6'03 ; of S. currents 27 : 190, or 1 : 7'03. Two N. as well as two S. currents were 
obtained ranging from 71° to 75°, and one N. current exceeding 80°; it was 82°. There 
is no very marked difference between the numbers of N. and S. for the different values 
on each day ; sometimes the N., at other times the S. are in the ascendent. Above 45°, 
26 N. currents are recorded against 22 S. 
The h dmsion of Table X. gives the mean value of the N. and the S. currents for 
each day, and the general mean of the whole. The N. on some days and the S. on other 
days have the higher mean value. The general mean gives 28°‘01 for the N. and 26°' 87 
for the S. currents. Taking the mean of all the currents, the values are 9-46 minutes 
of time (Table IX. c), and 27°’44 of deflection (Table X. V). 
The Tables we have now been discussing may be taken as good specimens of the 
