344 
THE REV. STEPHEN J. PERRY ON THE MAGNETIC 
l-484=&-53-4ff-14% 
l-970=&- S+r+18% 
l-920=&-14*3a?+ 2% 
1-736=5— 4-7;r+12% 
1- 591=& + 18*6s-27% 
+557=&-2D3tf-26% 
2- 228=^+63-0^+26% 
l-672=o-65-2^-25-5y 
1- 650=S+43+r-17% 
2- 378=^ + 30-8^ + 13-8^ 
2-134=^-23-7^+32% 
1*738=&— 65*Lr— 17% 
The solution of these equations of condition, found by the method of least squares, is 
5=1-87299, +=00013762, y= -0-0104147. 
The computed value of the Dip at the central station is therefore 66°-87299, the 
direction of the Isoclinals being from N. 82° 28' 19" ’4. E. to S. 82° 28' 19"*4 W., and the 
distance between stations, whose Dips differ by 0 o, 5, 47*6 miles. 
The Dip at the several stations obtained from this calculated data, and compared 
with the observed mean values, furnishes the following Table of errors : — 
Table III. 
Station. 
Observed Dip. 
Computed Dip. 
Errors. 
Aix-la-Chapelle 
1-657 
1-708 
-0051 
Alost 
2-22(5 
1-954 
+0-272 
Antwerp 
2-022 
2136 
-0114 
Arlon 
0-926 
0-943 
-0-017 
Bruges 
2-172 
2-198 
-0 026 
Court-ray 
1-696 
1-912 
-0-216 
Ghent 
2-239 
2-056 
+0-183 
Liege 
1-484 
1-654 
-0-170 
Lierre 
1-970 
2051 
-0-081 
Louvain 
1-920 
1-880 
+0040 
Mechlin 
1-736 
1-994 
-0258 
Mons 
1-591 
1-608 
-0017 
Namur 
1-557 
1-566 
-0-009 
Ostend 
2-228 
2-229 
-0-001 
Spa 
1-672 
1-517 
+0-155 
Tournay 
1 650 
1-754 
-0104 
Tronchiennes 
2-378 
2-059 
+ 0-319 
Turnhout 
2 134 
2-174 
-0 040 
Verviers 
1-738 
1-601 
+0-137 
The probable error at any one station will therefore be +0-10445, whilst that of the 
mean Dip at the central station is +0-02185. 
Deferring now to previous observations, we shall be able to ascertain approximately 
the secular variation of the Dip. The only determinations of this magnetic element 
for stations out of Brussels are those of M. Mahmoud Effendi in 1854 and of 
Dr. Lamont in 1858, and these will serve to form the following Tables. 
