456 Rey. Mr. Luoyp on a New Method of Observation 
III. October and November 1835. 
Place Date Hour ‘Temp. (Z) ; (6) 
London Oct. 23 Tess 50°5 69° 106 |— 16° 32/0 
— See 51.6 69 2.2)}—16 35.4 
24 1 16 53.8 69 6.0 |—16 44.4 
Mean 52.0 69 63 |}—16 37.3 
Dublin Noy. 5 i2> 522 56.2 70 49.6 |—12 54.6 
— QO. f32 52.8 70 45.8 |—12 54.5 
6 TE Pcie) 49.0 70 53.9 |—12 36.6 
Mean 52.7 12 48.6 
London, Dublin. 
Z=) 60° 36.3) 6 ere t= 70° 40'.8, «= +15 
Js Wolth ygick oa /0 51.3. 
0=—16 37.3, log cos = 9.98146 6=—12 48.6, log cos = 9.98905 
$-0= 85 45.1, log sin = 9.99881 8—0= 83 39.9, log sin = 9.99734 
diff. = —.0O1735 diff. = — .00829 
fess SEP OP corr. = —.00055 r—t=— 7. 3, corr. =— .00050 
A, = -.01790 A = — .00879 
log ¢=A—A,= +.00911, $= 1.0212. 
In order to reduce these results to the same epoch, the values of the dip obtained 
in the autumn of 1834 must be diminished by 3’, that being nearly the amount of the 
annual decrease of dip in this part of the globe at the present time. We have then, 
on summing up, 
(8,) (8) (9) 
I. 69° 5.9 70° 52.1 1.0196 
II. 69 12.6 70 52.4 1.0217 
69 7.8 70 51.3 1.0212 
69 8.8 70 51.9 1.0208 
We may now compare the preceding determinations of the Intensity with those 
obtained by the received method. We have for this purpose three comparisons of the 
horizontal part of the magnetic force at Dublin and London, made in the summer and 
autumn of last year; the latter two having been cotemporaneous with (II) and (III) 
of the preceding table. The results of these comparisons are given in the annexed 
table, which contains 1. the place, and 2. the date of the observation ; 3. the name of 
needle employed ; 4. the number of observations ; 5. the mean time of 100 vibrations, 
corrected for temperature and for the rate of the chronometer; and 6. the computed 
ratio of the horizontal intensities. The observations were made in the manner adopted 
by Professor Hansteen, viz. by allowing the needle to make 360 vibrations com- 
Da, 
arp, 
