the comet of 1807 appear to countenance this theory), the objections relative to their being habitable, on account of the extremes of heat and cold to which they were supposed to be subject, will lose all their force; and it must be admitted, that each is susceptible of affording sustenance and enjoyment to myriads of rational and intelligent beings.

From a serious reflection upon the facts that have been stated, and the observations that have been offered, not only in the preceding parts of this volume, but in the course of the whole work, will it not appear that the opinion of those who maintain that all the vast globes which with us roll round the Sun, and with us participate in his vivifying influence, are desolate and destitute of inhabitants, is unsupported by reason, and unworthy to be classed among the deliberate sentiments of a rational and thinking being? While the contrary supposition exalts the wisdom and benevolence of creative design, and magnifies the goodness of a superintending Providence far beyond our utmost conceptions; and includes all created nature in that harmonic order which characterizes those minute parts which fall more immediately under our contemplation. Viewing this vast assemblage of moving bodies as being all regulated by the operation of one general law, induced the celebrated M. Lambert, above referred to, to exclaim, What a delightful, what an enchanting, spectacle is this immense machine, which goes on and maintains its infinitely diversified motions by the most simple of all laws, by the sole principle of gravitation! This is the master-piece of creative intelligence; an object of admiration to men and angels !'

On the MOTION and ABERRATION of LIGHT.

Having treated of the various heavenly bodies which are perceived either by direct or reflected light, we shall now offer a few observations relative to that substance or medium which not only renders them viBb

sible, but embraces the whole of the universe in its action. M. Hauy has justly observed, that there is no branch of philosophy more deserving of our study than light, whether we consider its beauty, or the multiplicity of phenomena it presents. The advantages we derive from the fluid that enlightens us are sufficient of themselves to excite the closest attention, that we may understand its various properties. If air, serving as the vehicle of speech, enables us to carry on an intercourse of thought with our fellowcreatures, how greatly is that intercourse improved by light, which renders their image present to us-their image, which has so many things to say! The eye, more susceptible than the other senses of multifarious impressions, by the aid of light takes in at once in bodies the forms by which they are limited, the colours that embellish them, their relative positions, and the motions by which they are transported from one point of space to another. It discriminates all those modifications that seem to sport in a thousand different ways in that vast diversity of objects to which a single look can extend itself.

Nor are these all the advantages we derive from its properties. Beyond the globes that shine over our heads, there are other luminaries which the eye is unable to reach on account of their immense distance, while near us a thousand organized beings equally escape our observation, from their minuteness. Light, by being bent out of its direct course by passing through transparent substances bounded by curvilinear surfaces, has enabled us to: perceive these two kinds of infinity, has opened to astronomy a new heaven, and a new field to natural history.'

Various opinions have been entertained relative to the nature of light, and numerous experiments and inquiries have been made respecting it; and there is not any branch of philosophy which presents a wider field for the exercise of human sagacity, nor

any in which the genius of Newton shines with greater lustre. But as it is in its effects rather than its nature that we view it in connection with astronomy, our remarks must be chiefly confined to them. The sacred historian makes light the first of created things, and the immortal Milton has expressed the same sentiment in one of the noblest invocations that poetry can boast :

Hail, holy light, offspring of Heaven first-born,
Or of the Eternal co-eternal beam,

May I express thee unblamed? since God is light,
And never but in unapproached light
Dwelt from eternity, dwelt then in thee,
Bright effulgence of bright essence increate.
Or hearest thou rather, pure ethereal stream,
Whose fountain who shall tell? Before the Sun,
Before the heavens thou wert; and at the voice
Of God, as with a mantle didst invest

The rising world of waters dark and deep,
Won from the void and formless infinite.

The following poetical stanza is also very expressive of our knowledge of its absolute nature, and of the general effects it produces :

Behold the light emitted from the Sun;
What more familiar, and what more unknown?
While by its spreading radiance it reveals

All Nature's face, it still itself conceals.

It is now generally admitted by philosophers that light flows directly from the Sun and other selfluminous bodies; and even the inconceivable velocity with which it moves was not sufficient to elude the all-searching power of genius, and has now become the subject of human calculation.

The idea of measuring the velocity of light was first suggested to the mind of M. Roemer, a Danish philosopher, by the eclipses of Jupiter's satellites, by which he perceived that light occupied about eight minutes in passing from the Sun to the Earth. As this is one of the most curious problems that has been solved by human ingenuity, and admits of a familiar illustration, we shall insert the following

from Professor Bonnycastle's excellent Letters on Astronomy.

Let A and B, in the following figure, be the Earth in two different points of its orbit, whose distance from each other is equal to the Earth's distance from the Sun; it is then plain, that, if the motion of light were instantaneous, the satellite I would appear to a spectator at A to enter into Jupiter's shadow SS, at the same moment of time as to another spectator at B.

H

D

C

S

B

But from a great number of observations it was found, that when the Earth was at B, the immersion of the satellite into the shadow happened sooner, by about eight minutes, than when the Earth was at A, and therefore the motion of light must be progressive, or such as would carry it through a space equal to the radius of the Earth's annual orbit in about eight minutes of time. So that if the Sun were annihilated, we should see him for eight minutes afterwards; and if he were again created, it would be eight minutes before we could observe him.

The same thing may also be shown thus: the instant when any of these eclipses will happen can be easily determined by calculation, because the times in which they perform their revolutions are known; and as it is constantly found by observation, that any one of the satellites is eclipsed about sixteen minutes sooner when the Earth is nearest to Jupiter than when it is farthest from him, it is evident that this must be occasioned by the time that light takes in moving through the diameter of the Earth's orbit ;

for that these accelerations are not owing to any inequalities in the motions of the satellites themselves, is plain, because they are always affected alike, in whatever parts of their orbits they are eclipsed.

2

This explication furnishes us with the solution of one of the most curious problems that ever was attempted; which is that of determining the velocity of light. The minutest particles which are thrown off from the body of the Sun, move through a space of ninety-three millions of miles in eight minutes ; which is about a million of times swifter than the motion of a cannon-ball, when it is first projected from the mouth of a piece of ordnance; a rapidity too great for the imagination to follow, or the mind to comprehend. And yet, prodigious as the motion appears, there may be stars whose light has not

reached us since the creation of the world. This is the universe of the poet :'

Without bound,

Without dimension, where length, breadth, and height,
And time and place, are lost.

[To be continued.]

The Naturalist's Diary

For NOVEMBER 1818.

At first,

How has great Nature's hand, that works unseen
Through the revolving seasons, changed the scene!
Stripped of its fruits and flow'rs and verdure gay,
Nor one autumnal beauty left, the Earth,
Wrapt in her dusky mantle, sees resigned
Stern Winter's wayward reign commence.
Chill rain incessant pouring, floods the fields;
And from opposing quarters mighty winds,
On the same errand bent, with busy hands,
Tear from the groaning woods the ling'ring leaves.
The rattling hail descends, undoubted pledge
Of frost and snow and tempest yet to come.

FOWLING, a Poem.

NOVEMBER is, usually, a very gloomy month, yet there are some intervals of clear and pleasant wea