ARTICLE XXVIII. 
Observations of the Magnetic Inclination at Gottingen. By 
Professor C. F. Gauss *. 
[From the Resultate aus den Beobachtungen des Magnetischen Vereins im 
Jahre 1841.] 
Ale 
THE Inclinatorium with which these observations were ob- 
tained was made by Robinson, and is the last instrument of the 
_ kind completed by that distinguished artist before his death. 
The vertical circle has an interior diameter of 241°169 milli- 
metres (about 9°5 English inches), and is graduated to ten mi- 
nutes ; so that every two divisions are 0°351 millimetre apart 
at their inner extremities. The divisions when viewed through 
a microscope, even with a considerable magnifying power, appear 
very perfect; by repeated measurement I have found their 
breadth = 0°024 millimetre, so that each covers nearly 41 
seconds. 
The diameter of the horizontal circle, measured between the 
) points where the extremities of the index meet the graduation, 
_ is 148 millimetres. The graduation is to half degrees, and the 
vernier gives single minutes. There is only one reading. 
_ On the vertical circle the graduation counts upwards and 
downwards to 90° from the two extremities of a horizontal dia- 
_ meter, an arrangement which may perhaps appear convenient 
in ordinary cases of observation, but which is liable to cause 
some confusion, or at least to render the registry more trouble- 
some and less clear, when a loaded needle is employed, or when 
the plane of observation is varied from that of the magnetic 
meridian. I therefore prefer either a complete graduation of 
360°, or 180° twice repeated ; and I have accustomed myself, 
when observing either in the lower quadrant on the left side, or 
on the upper quadrant on the right side, to write down, instead 
of the division on the circle, the complement to 180°, and all the 
readings in this memoir are to be so understood. On the hori- 
zontal circle the numbers run twice in the same sense from 0 to 
* Communicated by Lieut-Colonel Sabine. 
VOL, III. PART XII. 2T 
