B. DECLINATION. 
The determination of the magnetic declination was made by the aid of 
two declination needles belonging to the apparatus, and furnished with mirrors, 
in a manner similar to that with an ordinary Neumayer-Declinatorium. After 
the instrument had been duly levelled, the telescope was pointed first at a 
mark, with subsequent reading of both verniers of the horizontal circle; and 
then a coincidence was effected, during the constant employment of the ivory 
disc, between the wire of the telescope and its reflected image in the mirror 
of the declination needle. From October 20th, 1895, to February 22nd, 1894, 
and on subsequent rare occasions, the telescope could not be used on account 
of fog, hoar-frost or unfavorable conditions of light. The setting was then 
done with the naked eye, a vertical line introduced in the middle of the 
glass of the magnet box, being employe das wire. The pin on which the de- 
clination needle rested, was renewed several times, as there was a reserve 
supply of pins, and also a special apparatus sent with the instrument, for 
grinding and polishing the point of the pin, if any injury should befall it. 
THE NEEDLES. 
THE DOUBLE DECLINATION NEEDLE. 
The needle intended for the declination observations proper, was a double 
one, that is to say, it consisted of two lamin, between which the mirror was 
fixed. Its weight was only 29.05 grammes, and as it was made to reverse, 
there was always an opportunity of determining, or eventually eliminating, 
