A. D. Bache on Magnetical Observations in Maine. 147 
diminution of the dip of 2'-2 in the first year, and of 3’0°in the 
second year. These evidences of a decreasing secular change 
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appeared at that time anomalous, but it will be seen that they 
are borne out by subsequent observations, and likewise in other 
places. The observations of the dip at Washington in 1860 
first tndicated a change of sign in the secular effect, which fact 
is now fully established by later observations, 
The values given in the following table for each month are 
the means of observations made on three, and sometimes on 
four days with two needles; the polarity of the needles was 
reversed during each set: 
Monthly means of magnetic dip. 
1860. 1861. 1862. 1863. 1964. 
t ’ Qo ’ 9 ’ 
Jan., 15 51-6 15 529 18 502 75 47-0 75 46-1 
Feb., 52-7 53-4 495 456 46-7 
March, 54° 52-7 490 474 467 
April, 54-4 521 49°3 490 446 
ay, 53°5 49°5 48-1 479 46-0 
June, 518 49-8 48-0 48°6 45°6 
July, 52-9 499 48-4 49°1 44:9 
54 504 482 50-6 
Sept., 512 48°3 498 
Oct., 533 50-9 492 49°5 
Nov,, 51-9 49°9 47-4 48-3 
Dee., 523 - 493 469 468 
Means, | 75 53'1 15510 | 76485 15483 
In July 1865 the dip was found from observations on four 
days, 75° 44-7, which, when reduced to the mean of the year, 
Zives 75° 448 for 1865. gee 
