applied to Terrestrial Magnetism. 455 
I. August and September 1834. 
Dublin | 
London. Dublin. 
t= 69° 7.4, c= +15 t= 70° 53.6, «= 41/5 
s8= 69 8.9. € oO —/ Ooo 
6=-—12 8.9, log cos = 9.99016 Oo Os log cos = 9.99579 
8-—0= 81 17.8, logsin = 9.99497 | 8-@= 78 53.0, log sin = 9.99177 
diff. = — .00481 diff. — + .00402 
tr—rTr=+8°.7, corr, = +.00060 | r—7 = +3°.0, corr. = +.00021 
A, = —.00421 A = +.00423 
log g=A—A, =+.00844, ¢=1.0196. 
IT. September 1835. 
Place : : (8) 
Dublin Sept. 4 1°56 71-8 70° 43.6 | — 12° 29.4 
5 2519 65.5 70 52.8;—13 15.4 
7 4 8 70.0 70 02.2} —13 20.8 
15 i Os) 62.0 70 55.0}— 13 10.5 
Mean 67.3 70 50.9|}—13 4.0 
London Sept. 19 1 10 68.0 69 74|/—16 54.2 
22 | 11 32 70.8 69 124|/—17 163 
Preity tena 70.0 69 13.6|—16 49.4 
Mean 69.6 (oo) | ET | i OX) 
London. Dublin. 
es 000g tell, a= +15 C=) 7 Ora50-95 e= F125 
8= 69 12.6. o= 5 2/0 524. 
6=-17 0.0, log cos = 9.98060 6=—-13 4.0, log cos = 9.98861 
8—0=86 12.6, log sin = 9.99905 8—0=83 56.4, log sin = 9.99756 
diff. = — .01845 diff. = —.00895 
t—r=+ 9.°6, corr. = +.00066 r—-r=+7.° 38, corr. = +.00050 
A, = —.01779 A = — .00845 
log ¢= A—A,= +.00934, = 1.0217. 
* The coefficient of r—r'in the correction, or the value of Ma, is .000069. 
VOL. XVII. 4K 
