\ 
398 
sionally fly, is probably not less than at the 
rate of 150’ miles in an hour ; the common 
erow, twenty-five ditto; tie swallow, ninety- 
two ditto, and the swift, three times greater. 
Migratory birds probably about fifty miles 
per hour.” 
I must beg leave to trespass so much 
further on your valuable space, as to 
express a complete disallowance of the 
distinction in the above quotation, be- 
tween the swallow and migratory birds, 
which seems to be inferred from the 
manner in which the sentence is worded, 
but which, perhaps, at the same time, 
was not actually meant to be asserted. 
Your’s, &c. THErmes. 
Allow me to add a brief notice of 
some observations in Switzerland, which 
tend to show that our continental neigh- 
bours are not altogether regardless of 
the interesting bearings of this ques- 
tion. 
Migration of Birds. — Dr. Schinz, 
Secretary to the Provincial Society of 
Zurich, has endeavoured to. discover 
the laws, according to which European 
birds are distributed. The country, in 
which the bird produces young, is con- 
sidered its proper one. The nearer the 
Poles, the more do we find peculiar, or 
stationary birds, and the fewer are the 
foreign species that appear. Green- 
land has not one bird of passage: Ice- 
land has only one, which remains dur- 
ing the winter, and, in spring, takes its 
flight to still more northern climates, 
Sweden and Norway have more; and 
we find them continually becoming 
more numerous, as we approach the 
centre of Europe. In the intertropical 
countries, no bird emigrates—to the 
north they all do: their propagation 
keeps pace with the supply of food. 
Spitzbergen, has only one herbivorous 
species, for the sea presents more nu- 
triment; and the rocks and cliffs are 
populous with aquatic birds, In the 
Frigid Zone, a much greater number of 
marsh birds breed, than beyond the 
Arctic Circle, and’in the warm coun- 
tries of Europe. 
————a 
For the Monthly Magazine. 
Extract of a REMARKABLE ANECDOTE 
relativeio the Arvrraction of the 
Heaventy Bopins, in Madme. Du 
Chastelet’s “ Exposition Abrégée du 
Systeme du Monde,” at the End of 
her Translation of Sir I. Newton's 
Principia. Vol. ii., p. 5, Art. VIII. 
RT. VUI. We find the attraction 
of the heavenly bodies still more 
Attraction of Heavenly Bodies. 
[Dee. 1, 
clearly mentioned in “ Hook’s Book 
on the Motion of the Earth,” printed 
in 1674, that is, twelve years before 
the Principia were published. Here is 
a translation ef what he (Hook) says, 
p- 27. 
“ Now I willexplain a system of the world 
which, in many respects, is different from 
all the others, and which is perfectly con- 
formable to the known laws of mechanies. 
Tt is founded on the three following hypo- 
theses, viz. 
Ist. “ That all the heavenly bodies, with- 
out exception, have an attractive force or 
gravitation towards their centres, by which 
they not only attract their own particles of 
matter and prevent their disunion, as we 
see it in the earth, but likewise attract all 
the other heayenly bodies that are within 
the sphere of their activity: whence it fol- 
lows that, not'only the sun and moon have 
an influence on the body and motion of the 
earth, and, reciprocally, the earth on them, 
but that Mercury, Venus, Mars, Jupiter 
and Saturn have also, by their attraction, 
a considerable influence on the motion of 
the earth, and, reciprocally, the earth a 
great influence on the motion of those 
planets. 
2d. “ That all bodies which have received 
a direct impetus, or impulsive stroke in 
any direction, will continue to move in a 
right line, and in the same direction, until 
they are turned aside, or made to deviate 
from it by some other effective force, and 
made to describe either a circle, an ellipsis, 
or some other, more complicated, curve. 
3d. “ That the said attractive forces are 
so much more powerful in their operations, 
the nearer they approach the centre of the 
body on which they act. 
“* With regard to the ratio in which these 
forees either increase or diminish, according 
as the distance decreases or increases respec- 
tively, I confess I have not yet ascertained by 
experience or observation ; but itis an idea 
which, if pursued with that attention I 
think it merits, will be of great serviee to 
future astronomers, in reducing the motions 
of the heavenly bodies to certain rule, which 
I doubt the possibility of ever effecting 
without it. Those who understand the 
nature of circular motion, and the gyration 
of a pendulum, will easily comprehend the - 
grounds of the above principles, and will 
be able to find out the means of establish- 
ing them on.sure foundations; I have here 
hinted this idea to those who have both tei- 
sure and abilities to render them successful 
in their researches,” &e. &e. 
Sir :—I think the. foregoing extract. 
worthy of notice; and, should you be 
of the same opinion, the insertion of it. 
in your next publication will oblige, — 
Your’s, &c.  Wittiam SHare. 
Romney, Oct. 13, 1825. 
For 
