xil INTRODUCTION TO THE MAKERSTOUN OBSERVATIONS, 1845 AND 1846. 
noted, and generally the director of the Observatory believes that he has an easy 
task in bearing the responsibility connected with the honest discharge of the duties 
of his assistants. 
DECLINOMETER. 
6. The declination magnetometer was obtained from Gruss of Dublin. The 
magnet a is 15 inches long, § inch broad, and 4 inch thick ; it fits into a stirrup 0, 
whose two eyes receive an axle to which the suspension thread is attached ; near 
the north extremity it carries a scale divided on glass, ¢; near the other, at a dis- 
tance from the scale of about 12 inches, the focal length, it carries a lens of 1} inch 
diameter, d. A marble slab m, cemented to the top of the stone pillar p, carries two 
copper tubes ff, 35 inches long, which are connected at the top by a mahogany 
tie g, bearing the torsion-circle and suspension apparatus ¢, and, about 7 inches 
from the slab, by another wooden cross-piece h, which supports a glass tube e enclos- 
ing the suspension thread. The magnet is enclosed by a rectangular wooden box k, 
formed of two pieces fitting into each other in the middle by a groove and tongue, 
glazed at the extremities, and having only a small aperture in the centre for the 
