XXXVI 
FIFTH REPORT— 1835. 
observations of these faint and often fluctuating meteors, than 
others of a more refined construction. 
2. It is recommended that a magnetic needle be kept in a 
proper place, suspended by a silk fibre or slender hair (a point- 
support not being delicate enough), and so mounted, that devia¬ 
tions can be observed to the accuracy of 1 ? . It has been found 
convenient to fix in a garden a stone pedestal, on which, at 
three invariable points, the frame of the magnetic needle rests 
under a glass cover. The needle, 9 inches long, and of such a 
weight as to perform about 10 vibrations in a minute, is sus¬ 
pended by one slender hair. There are simple contrivances to 
steady the needle when required, and to adjust the length of the 
suspending hair. The scale is divided in degrees for 30° on 
each side of the centre, and in 10 7 for 1° on each side. There 
is no vernier, but the place of the needle on the scale is read off 
with great ease by looking through a fixed magnifying-glass 
from an opening at some height above, so as to avoid sensible 
parallax. Professor Christie has described more complete ap¬ 
paratus for this purpose in the Journal of the Royal Institu¬ 
tion , New Series, vol. ii. p. 2/8. The observer must leave his 
watch with the assistant, very carefully remove all keys, knives, 
and other things containing iron from his dress, and all loose 
iron tools and utensils to at least 20 feet distance from the 
needle. If these precautions are not scrupulously attended to, 
the results will be fallacious. It is proper to caution the obser¬ 
ver that there is a regular daily variation of the needle, inde¬ 
pendent of the Aurora. 
Dipping-needles , unless constructed with the utmost care, 
cannot be considered very satisfactory instruments; yet, if 
their suspension be sufficiently delicate, they may probably very 
well answer for observations during Aurora, of which the object 
is to determine, not the absolute dip of the needle , but the 
change of dip occasioned by the Aurora. The same precautions 
of one certain position, removal of iron, &c. are necessary, as in 
the use of the horizontal needle. 
3. It is recommended that arrangements be made for ascer¬ 
taining the error of a watch. If near an observatory of any 
kind, the watch should be compared with the transit clock there 
immediately after an Aurora; if there is a good meridian line, 
or good dial, the error of the watch on mean time should be 
found as soon as possible ; if a watchmaker in the neighbour¬ 
hood has a good regulator, the watch should be adjusted by it, 
and the mode of keeping the regulator should be ascertained; 
if a mail-coach from London passes near, the guard’s watch 
may be consulted. The longitude of the place of observation 
