xii 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 Grubb of Dublin. The 

 magnet a is 15 inches long, f inch broad, and \ inch thick ; it fits into a stirrup 6, 



whose two eyes receive an axle to which the suspension thread is attached ; near 

 the north extremity it carries a scale divided on glass, c ; 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//, 35 inches long, which are connected at the top by a mahogany 

 tie ^, bearing the torsion-circle and suspension apparatus t, and, about 7 inches 

 from the slab, by another wooden cross-piece A, 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 



