212 
ticable, muft be afcertained by the com- 
pals. The angles may thence be moft 
conveniently taken with the fextant, to a 
degree of perfe€tion attainable with no 
other portable inftrument. 
I have the pleafure to add, that the 
principles of both inftruments have receiv- 
ed the unanimous approbation and fanc- 
tion of many uluftrious and {cientific naval 
characters ; amongft whom I have the 
honour to include the armes of Sir Sidney 
Smith, Commodore Truxton, of the 
American marine, Dr. Mackey, &c. &c. 
Tam, &c. E. HoprPr. ~ 
~ Mathematical Inftrument-maker, 
Courchfircet, Minories, Feb. 16, 1805, 
=e 
Yo the Editor of the. Monthly Magazine. 
SIR; 
ITH the return of fpring, I think 
it proper to thank my obliging and 
intelligent corre{pondents on the fubjeét 
of my inquiry relative ‘te the {wallow- 
tribe, and to requeft naturalifts will have 
the goodnefs to communicate to me their 
farther obfervations on the appearance and 
habits of thefe interefting birds, whofe 
period of activity is {peedily approaching. 
I am happy to fay, that I have already 
been favoured with a large mafs of infor- 
mation ; but on a fubject that has exer- 
cifed the ingenuity and baffled the inquiry 
of naturalifts for numerous ages, it is not 
to he fuppofed, that the exertions of a 
few, and during a fhort period, can be 
fuficient to remove the veil which has fo 
jong concealed from our eyes the manner 
in which {wallows pafs the winter-months, 
and the place to which they retire. 
Among the aumber of my kind and 
intelligent correfpondents, who, I have no 
doubt, are all equally animated with the 
love of truth,, 1 find fome who ftrecuoufly 
maintain the migration of the fwallow- 
tribe, and others who as ftrenuoufly 
maintain the contrary pofition. But it is 
not by theory, but by faéts attentively 
obferved, and. faithfully reported, that 
this queition can be decided ; and though 
it would be premature in me to hezard ° 
2ny opinion in the prefent ftate of the 
inguiry, Iam candid enough to confefs, 
that the weight of evidence feems in favour 
ot {wa.lows lying torpid during the pe- 
riod of their difappearance. 
Some curious, and, I believe, authen- 
tic, inftances of this kind have been com- 
municated.to me , but, from want cf a 
due attention to the diferimination of the 
ipecies difcovered in a Gormant, ftate, 
much uncertainty ftill hangs over this 
interelting fubjeé&t ; and I anxioufly and 
ardently requeft, that the lovers and ob- 
fervers of natuie, who may be pleafed to 
¢ 
Dr. Mavor on Hirundines, 
[ April 1, 
favour me with their correfpondencey 
-will endeavour, as far as lies in their 
power, to afcertain the fpecies to which 
they refer, which being eafily diftinguifh- 
ed, will effentially contribute to eftablith * 
faéts and to remove doubts. 
I am aware that it is unfafe to carry 
analogy too far in regard to natural hifte- 
ry ; but when it is confidered that the 
hiftory of the individual animal in a ftate 
of nature is the hiftory of the fpecies, it 
feems reafonable to infer, that if a certain 
number of fwallows of any determinate | 
{pecies poffefs the faculty of lying torpid 
during the winter, and of reviving with 
the return of fpring, there can be no ne- 
ceffity to have recourfe to migration with 
regard to the reft. Befides, if it be al- 
lowed that fwallows migrate to warmer 
regions, in order to enjoy that food which 
becomes deficient here, what inducement, 
it may be afked, can they have to leave 
the mild climate of Madeira, which [I 
have lately been affured, by a very intelli- 
gent Englifh phyfician long refident there, 
is actually the cafe, in the fame manner 
as with us? Has not this been obferved, 
too, in Greece, from remote antiquity ?—= 
And, as far as information has been laid 
before the public, does it not appear that 
this may be affirmed of {wallows in every 
other country, whatever may be its tem 
perature ? 
There may be a fufficient, as there is 
an obvious, reafon, for birds that breed 
and pafs their fummers in the northern re- 
gions, to migrate here when their native 
lakes and rivers are frozen, and the 
ground univerfally covered with fnow 5 
but what caufe can be afligned for fwal- 
lows (even admitting their migration) re- | 
turning from regions where infeét-food 
mutt always be comparatively more abun- 
dant, and that, too, at fuch an early fea- 
fon, when it is with difficulty they can 
pick up the means of fubfiftence here ? 
As the elucidation of truth, however, 
and not the fupport of any hypothefis, is 
‘the object of my inquiry, thefe hints are 
thrown out merely: to excite the attention 
of naturalifts to the points in queftion.— 
If, in the event, I fhall fortunately be en- 
abled to come to any decifive conclufion, 
the faéts on which it is eftablifhed it~ 
wiil be my ftudy to Jay faithfully before 
the public ; and if, after all my pains, 
and the. communications with which I 
may be favoured, I feel it proper to hefi- 
_tate, I fhall in that cafe, too, confider it 
as my duty to fum up the evidence pre 
and coz, and leave the jury of the pubN= 
to bring in their verdiét as alove of treth 
may dictate. _ W. Mavor. 
Woodjiock, March 10, 1805. q, 
. Te 
