74 
Mr. Be van's observations on the heights of places 
strong ground for supposing a deflection of the plumb-line 
to the southward. To ascertain if this supposition were sup- 
ported by the trigonometrical operations, I calculated the 
latitude of Arbury station, from the latitude of Blenheim, as 
detennined by previous observation, independent of any as- 
tronomical observation made at Arbury, and find it 5 seconds 
less than shown by the zenith sector ; giving countenance to 
the probability of local attraction by the high land to the south 
of the station, which will appear by the following calculation ; 
in Trigonometrical Survey, Vol. 2, p. 137, the latitude of 
Blenheim by observation is stated as 51 0 50' 24". 9 or nearly 
51 0 50' 25". 
The measured distance, on the meridian, from Blenheim to 
Arbury, is 139822, deduced from Vol. 2, part 2, p. 107 ; di- 
viding this distance by 60881.7, according to a table in Vol. 1, 
part 1, page 168, corresponding to the middle latitude be- 
tween Blenheim and Arbury, and multiplying the quotient 
by 10. we obtain the difference of latitude = 0 22' 58". 
this quantity added to - - - - 51 50 25 
gives for the latitude of Arbury - - - 52 13 23 
being 5" less than by the zenith sector. It is true that Colo- 
nel Mudge corrected the latitude of Blenheim, from the Tri- 
gonometrical Survey, to 5i°5o'28", and in this case the com- 
puted latitude of Arbury would come out near 3 seconds less 
than found by the zenith sector. In Vol. 2, part 1, page 118, 
the latitude of Arbury, as derived from Dunnose meridian, is 
given - 52°i3 / 26 // .6 
afterwards 52 13 28 .2 from observation* 
1 .6 or i{ second south of the observed 
* Vol. 2 , part 2, page 109, Dunnose is stated to be . . 50° 37' 8",2 
p. 107, from Dunnose to Arbury is . 1 36 19,98 
52 13 28,18 
