INTRODUCTION. xl 
1841, to conduct the Observatory, and resigned in April 1842. Mr RUSSELL is, 
therefore, only responsible for the observations up till that period.* 
During term-days, Mr RussELL was assisted by Mr P. Apr of Edinburgh, 
Mr Hoee of Kelso, and myself. After the April term 1842, Mr Dons, teacher 
of Makerstoun parish school, replaced Mr RussEL1 in the term observations ; and 
after the term 1842, Mr CutsHoim, teacher of Maxton parish school, replaced 
Mr ADIE. 
The Daily and Extra Observations, and Observations of Adjustment, till the 
end of April 1842, were made by Mr RussELL, assisted in some of the latter by me. 
MAGNETICAL INSTRUMENTS. 
§ 3. DECLINOMETER. 
7. The Declination Magnetometer was obtained from Gruss of Dublin. The 
Magnet is 15 inches long, gths of an inch broad, and 4th inch in thickness. It fits 
into a stirrup, whose two eyes receive an axle attached to the suspension thread. 
At the north extremity, it carries a scale divided on glass; at the other, about 12 
inches distant (its focal length), a lens of 14 inch diameter. 
A marble slab cemented to the top of the Declinometer-Pillar, carries two 
copper tubes, which are connected at the top by a wooden tie, bearing the Torsion- 
Circle and Suspension Apparatus. 
The Suspension Thread, formed of sixteen fibres of untwisted silk, is enclosed 
by a glass tube; and the Magnet, with copper ring, for checking the vibrations, by 
a cylindrical box, with glass lids. There are two glazed apertures in the sides of 
the box, one to the north, where a small mirror throws light upon the glass scale, 
the other to the south between the Lens and the Reading Telescope. 
_-The ing Telescope is fixed to its pier. By noting the coincidences of the 
Scale divisions with the vertical wire at the eye-glass of the telescope, the variations 
of the position of the freely suspended magnet are obtained. 
* Mr Roussexz studied the methods of observing, &c., at Dublin, under Professor H. Luoyp, to 
whom he was also indebted for his attention to various difficulties which were subsequently met with. 
To Professor Liuoyp I also owe my acknowledgments for his attention to several of my own com- 
munications. 
Professor Luoyn, at the desire of Sir Tuomas BrisBanz, likewise examined the observations made 
by Mr Russetx and by myself till October 1842. 
To Mr Airy, Sir THomas BrisBane’s thanks, and my own, are due, for the facilities afforded 
me at the Royal Observatory, Greenwich, in April 1842, of acquiring a knowledge of the methods 
adopted there. I should not omit to mention my obligations to Lieut.-Col. Sasrve, and Professor 
Forzss, for their advice on some occasions. 
