74 
Capt. Parry and Lieut . Foster's 
The needles, distinguished by Nos. i and 2 in the follow- 
ing tables were suspended, instead of supported, and were con- 
tained within a small wooden box having a glass cover. The 
centre of each was made exactly to coincide with the centre 
of motion of the index of a common Hadley’s quadrant, gra- 
duated to minutes as usual, the box being fixed upon the index 
and moving with it. The agate cup of each needle was 
just allowed to touch a fine steel point of support, in order 
to preserve their correct centres. No. 1 needle belonged to 
an azimuth compass on Capt. Kater’s construction, its 
lozenge shape being that figured in the Appendix to the 
Voyage of 1819-20, p. cix ; except that this needle was 
rounded at the corners forming the extremities of its trans- 
verse diameter. Its weight (with the addition of mica ends 
increasing its length to eight inches for the purpose of more 
accurate observation) was 104 grains, that of the needle 
alone being 50 grains. 
No. 2 needle was formed of clock spring, and furnished 
by Mr. Christie, for some experiments to be made with it 
under the influence of magnets. Its shape has been already 
described by that gentleman in his paper on this subject, in 
the Philosophical Transactions for the year 1823. 
The length of this needle was 4,9 inches, but increased by 
mica ends to about ten inches, in which state it weighed 
96 grains, that of the needle alone being 51 grains. 
Both these needles were delicately suspended by a few 
fine threads of floss silk, from seven to eight inches in 
length, having no torsion, and passing up through a copper 
cylinder over a small brass pulley. A leaden weight just 
equivalent to that of the needle was then attached to the 
