A. D. Bache on Magnetical Observations in Maine. 143 
Diurnai range of the declination,—The difference between the 
maximum and minimum value of the declination set down in 
the table for each month, is the mean of four days of observa- 
tions. 
Means erved, Cor. for Mfrs gs 
iseo. | 1861. | 1962 | 1863. | 1964. { of ee ainual {21 yonre. 
5 years. inequality, ‘inequality lanaaleed, 
Jan, | 152] 86 | 121] 106] 11-4] 116 | -#1 | -64 | 85 
Feb. 12°6 11-7 110 8-0 9:0 105 -3°2 -9°3 —3°5 
March,} 16°4 18-1 13-1 11°8 13°0 14°5 +0°8 -0-2 +06 
April, rhe 136 18-4 166 116 15°2 +15 -O'1 +14 
May, 18 8-8 14:2 156 15°9 14 +0°9 00 +0°9 
June, 18: t 12'S 17-7 15:5 13°2 154 +17 0:0 +17 
July, 13:0 163 17°8 14:6 13°6 15:1 +14 00 +14 
Aug., 21-5 18:7 19°8 14:5 in 18°3 +4'6 00 +4°6 
Sept., 19-5 188 174 | 155 eee 17°5 +3'8 +01 +3°9 
Oct., 18-7 10-4 141 14-2 ‘eae 14:0 +03 +2 +0°5 
Nov, 13°97 9-2 8-9 8-9 9°9 -3'8 +0 -3°5 
Dee., 7-8 9-0 8-0 6-4 fase | 75 -6°2 +04 -58 
Annual ; : : i | 
Means, 15-9 13-0 14:4; 12-7 pg | 137 
The average difference between the 7 values of 1864 and the 
mean of the 4 years preceding is —1’6. Applying this to the 4 
sage means for the remaining five months, the interpolated means 
1864 become, for Aug. 17-0, for Sept. 16'°2, for Oct. 12”8, 
for Nov. 8'-6, and for Dec. 62. The column headed * means of 
5 years” is ssutphaaatl with the aifl of these values. The inter- 
ha mean for 1864 is 12°4. The pear annual change 
0"-9, 
The 11 year inequality in the range of the <a bi ogi 
appears quite plainly in py annual means. The y 
€ of maximum and 1866 of minimum, sbsohdiniy a the on 
servations of the solar spots; in 1865 the average range will, 
therefo ore, be a little above 12’, and in 1866 a little below this 
value. giving a range of variability due to the 11 years inequal- 
ity of nearly 4’. The corresponding ee ans a tae 
the petal yet eriod, a correction iia therefore been apie 
to obtain the annual inequality in the diurnal range free from 
the cahes year period as shown in last column of above table. _ 
The annual inequality of the diurnal range at Eastport and 
Philadelphia compare as shown by the annexed diagram, the 
full line being for Eastport, the broken line for Philadelphia. 
he Toronto curve also agrees well with these curves. 
