D. INCLINATION. 



When the NEUMAYER magnetometer is to be employed for the determi- 

 nation of inclination and total intensity, the magnet box, and the telescope, 

 as indicated in the introduction, are removed, and upon the alhidade of the 

 horizontal circle is fixed a vertical circle, intended for this purpose, and con- 

 structed like a Fox apparatus. For the purpose of deflecting the inclination- 

 needle, two cylindrical magnets are to be screwed into the alhidade on the 

 back of the circle as deflectors. There are two inclination-needles belonging 

 to the instrument designated as B and jB 1 . Of these two, the needle B 

 is stated in Dr. NEUMAYER'S manuscript to be the most reliable, and it has 

 therefore been used in the great majority of cases. There are in all 92 

 series of observations for the determination of the inclination, only 4 of 

 these being with needle B , The observations were made in the usual 

 manner, care being taken to observe the prescribed precautions, namely, 

 constant rubbing with the ivory disc, turning the bracket by means of the 

 screw-head at the back of the circle, cleaning the pivots with elder pith, 

 and the cleaning of the needle itself and the pivot-holes. 



The meridian reading was first determined on the horizontal circle by 

 four settings in the magnetic prime vertical, both the north and the south 

 end of the needle being brought into coincidence with the circle's vertical 

 points, 90, in both positions of the instrument designated as "Circle N" and 

 "Circle S". In the next place, a series of inclination-readings were taken in 

 the two positions of the instrument designated as "Circle E" and "Circle W". 

 As the needles were always used in the same position, with the marked 



