SURVEY OF BELGIUM IN 1871. 
345 
Table IV. 
Station. 
Dip, 1854. 
Dip, 187L 
Diff. of Epoch. 
Diff. of Dip. 
Yearly rate. 
Antwerp 
67875 
67-022 
17 
-0-853 
-0050 
Courtray 
67-655 
66-696 
-0-959 
-0-056 
Ghent 
67833 
67-239 
,, 
—0-594 
-0036 
Mons 
67-383 
66-591 
-0-792 
-0047 
Ostend 
68-047 
67-228 
-0 819 
-0048 
Brussels 
67-663 
66-994 
-0669 
-0039 
Mean for 1862-5... 
-0 046 
Table V. 
Station. 
Dip, Jan. 1, 1858. 
Dip, Sept. 1, 1871. 
Diif. of Epoch. 
Diff. of Dip. 
Yearly rate. 
Aix-la-Chapelle 
67-445 
66-657 
m 
-0-788 
-0058 
Ghent 
68002 
67-239 
„ 
-0763 
-0 056 
Mechlin 
67 643 
66736 
,, 
-0-907 
-0066 
Brussels 
67663 
66-994 
-0669 
-0-049 
Mean for 1864-8... 
-0 0573 
The values for Ghent and Brussels in the first column of figures of Table IV. do not 
inspire much confidence, as the latter is identical with Lamoxt’s value for 1858 ; and the 
former is much smaller than the corresponding number in Table V., although observed 
four years previously. 
Table V. gives a secular variation which lies about midway between the values 
— 0062 and — 0*054 found respectively for the West and East of France. Table IY. 
would make the secular variation — 0*050, if we neglected the two doubtful quantities. 
Dr. Lamont gives — 0*0417 as the annual decrease for 1858, which would indicate an 
acceleration of the yearly rate. We know, however, from the continuous series of obser- 
vations made at the Brussels Observatory, and published in its ‘ Annuaire’ by the eminent 
Director, M. A. Quetelet, that the annual decrease has been gradually diminishing from 
0°*0527 in 1830 to 0°*0194 in 18G5, the yearly variation being 0*00095. The extreme 
values of the Dip observed at the Boyal Observatory at Brussels were G8° 5G'*5 in 1827*8, 
and G7° S'*0 in 1871*5. 
