350 
THE EEY. STEPHEN J. PEBEY ON THE MAGNETIC 
Namur, Liege, and Aix-la-Chapelle, whilst the remainder of the country appears to be 
wholly devoid of all ferruginous wealth. 
As a further series of observations in this region might throw considerable light on 
the subject of local magnetism, I purpose, unless the work is previously undertaken by 
others, again to observe the magnetic elements at closer stations within this interesting 
area. 
If the disturbing cause is unchangeable, it will probably not interfere much with the 
determination of the secular variation of the Intensity as given in the annexed Table. 
Table XII. 
Station. 
T.E., Jan. 1, 1858. 
T. E., Sept 1, 1871. 
Diff. of Epoch. 
Yearly change. 
Aix-la-Chapelle 
10-2586 
101064 
-0-01114 
Ghent 
10-2923 
101268 
. 
-0-01211 
Brussels 
10-2869 
10 1310 
» 
-001141 
Mean for 1864-8... 
-001155 
The Magnetic Declination. 
In the observations for determining this element the azimuth of the fixed mark was 
found by taking transits of the sun with a transit-theodolite by Simms, kindly placed at 
my disposal for this survey by J. Siioolbred, Esq., C.E. ; and the angular distance 
between the mark and the magnetic meridian was read on Jones’s unifilar. The same 
tripod served for both instruments. Before observing the sun, the fixed mark was 
bisected by the wire of the telescope, when the verniers of the azimuth-circle read 0° and 
180°; thus the figures in the 6th column of Table XIY. are either the means of the 
readings as taken, or their defect from 360°. 
The same magnet was used for all the observations, and each entry is the mean of 
the readings with erect and inverted scale. The scale-coefficient is 2' Q'^SOS. For the 
o 
observations at the Boyal Observatory, Brussels, on the 9th of August, the zero-mark 
was not determined by observed transits with the theodolite, but a plumb-line was 
suspended in the meridian in front of the magnetic hut by aid of the large transit 
instrument of the observatory, and then the unifilar was adjusted in the meridian as 
accurately as this method would permit. The chronometer used was Frodsham’s 
No. 3148. The following Table contains the results of the comparisons made at 
Brussels and Stony hurst : — 
Table XIII. 
Station. 
Date. 
G. M. T. 
Error. 
Daily Rate. 
1871. 
h m 
m s 
Stonyhurst Observatory 
July 31 
7 30 p.m. 
+ 28 44-62 
+3-09 
Brussels Observatory 
Aug. 9 
7 30 „ 
+29 15-10 
+3-39 
„ ,, 
Sept. 22 
7 30 „ 
+32 21-90 
+4-25 
Stonyhurst 
„ 29 
11 0 „ 
+32 45 01 
+3-24 
)» 
Oct. 3 
10 0 „ 
+32 55-69 
+2-69 
