On determining the Latitude of a Place ly the Pole-Star. 445 
less injury to the tree than suffering it to attain its growth. But 
the mode which I should recommend in this, as in the case of 
almost all insects injurious to the horticulturist, is to employ 
children in the summer months to destroy the moths themselves, 
- giving a small premium for every ten or twenty they collect ; and 
increasing it as the numbers become lessened. When taught 
where to look for tnem, they would discover numbers on the bark 
of the trees ; and, if provided with gauze clasp-nets, would find it 
a most healthy and interesting occupation to catch them when 
made to fly by shaking the trees and bushes in which they re- 
pose. The destruction of every female moth, before the depo- 
sition of its eggs, may be fairly calculated to prevent the exist- 
ence of some hundreds of larve ; and thus in any garden not in 
the neighbourhood of others where the same methods are neg- 
lected, the whole race might in a few years be extirpated. 
XCI. On a new Method of determining the Latitude of a 
Place by Observations of the Pole-Star. By Francis Bairy, 
Esq. F.RS.* : 
Ir is well known that the usual mode of deterinining the lati- 
tude of a place is by observing the zenith distance, or the alti- 
tude, of the sun or certain of the fixed stars at the precise mo- 
ment of their passing the meridian. But, although this point of 
time might appear the most favourable for such observations, 
yet, by the assistance of a refined analysis, the modern astrono- 
mer has been enabled to extend the period of such observations 
to several minutes on each side of the meridian ; and the results 
are, by the help of certain tables constructed for that purpose, 
rendered as correct as those which are taken immediately at 
the time of culmination. 
Of all the stars which have been observed for this purpose, 
none have engrossed so much the attention of astronomers, as 
the pole-star: and, in fact, it is almost the only one which is 
now resorted to on such occasions, Its proximity to the pole 
renders it highly favourable for such observations in this hemi- 
sphere; it being on that account, and from its magnitude, visi- 
ble (with telescopes of no very considerable power) at all times 
of the year, by day as well as by night. 
But there is another important advantage to be derived from 
its small polar distance, which, till of late years, appears to have 
escaped the attention of astronomers ; and which it is my ob- 
ject, in the present communication, to point out to those who 
may not have considered the subject: viz. that the latitude of a 
* Communicated by the Author. 
place 
