MAGNETIC INCLINATION AT GOTTINGEN. 631 
I select for the purpose the observation with needle 1 on 
the 23rd of September 1842, from 8} to 11 a.m. The instru- 
ment was placed in the magnetic meridian by the aid of an 
auxiliary needle in the manner indicated in article 6, and the 
index of the azimuth circle (the degrees of which are reckoned 
uninterruptedly from left to right, and by me, as before noticed, 
from 0° to 360°) pointed to 90° 5! when the vertical circle was in 
the meridian, and the graduated face was turned towards the 
east. 
Besides the eight usual combinations in the magnetic meri- 
dian, I made on this day an equal number in the vertical plane 
normal to the meridian; these latter observations are here in- 
cluded, as they give occasion to several investigations. The 
needle employed (as well as the other three) is marked on one 
side with the letters A and B at either end, forming a convenient 
distinction both in reversals of the poles and of the faces of the 
needles. In each of the sixteen combinations the needle was 
raised and lowered on the agate planes five times by means of 
the Y’s; the following table gives only the mean numbers in 
each position. 
End B a North Pole. 
Marked face of Needle. 
Azim. To the front. To the back. 
circle, 
Lower. Upper. Lower. Upper. § 
° 4 (oN aaa (omen Row ° veer? ° A th 
90 5 67 27 54 67 29 36 67 45 39 67 44 51 
180 5 89 52 39 89 52 51 90 12 30 90 10 380 
5 
5 
270 112 18 89 | 112 16 45 112 38 51 | 112 33 54 
0 89 58 33 89 57 48 90 13 27 90 10 54 
End A a North Pole. 
90 5 68 2 51 68 2 33 67 35 15 67 37 (0 
180 5 90 14 48 90 12 21 89 51 12 89 51 36 
970 5 | 112 27 21 12 22.33 112 7 6 1125 33 
0 5 | 90 16 15 90 14 0 | 89 53 54 89 54 18 
The duration of one horizontal vibration was found— 
before the observations ..... 5883555. 
after the observations ...... 5 °87416. 
10. 
I will consider first the differences between the readings of the 
upper and lower ends, which arise from the axis of rotation not 
passing either through the centre of the graduation, or through 
the straight line which unites the two extremities of the needle. 
If we make x y signify the coordinates of the intersection of the 
