ours, though possibly not all, but yet others instead thereof, not less valuable. Nor would they seem less wonderful and pleasant to us, could we be transported thither by some powerful genius, which since he despairs of, he endeavours in his second book to give us his judgment concerning the phænomena of the heavens, what they might appear to one of us supposed to be there in one of them, which he founds on the knowledge we now have of them, as to magnitude, distance, &c. And here, after he has censured Father Kircher's Iter Extaticum (a book published on the like subject) he begins to tell what must be the phænomena of the sun and planets, seen in, and next what the same must be seen in Venus, which since with a sixty foot telescope, and all his diligence, he could never discover to have spots, or differently illuminated parts, as are visible in Mars, Jupiter, and Saturn. He conjectures that the reflection of light from it is made by the atmosphere about it, and not by the body itself. Thirdly, what they are in Mars, which he makes much less than Venus, or the Earth, though without a moon, and further distant from the sun. And, Fourthly, what in Jupiter and Saturn, which so vastly exceed all the other three, both for their magnitude, and for their concomitants, Jupiter having 4, and Saturn 5, together with a ring, whereas the Earth has but one, and the other three none at all. Upon explaining the phænomena of these, he more largely insists, and has therein summed up all the latest and best phænomena that have been observed concerning them, as to the five moons about И, though he confesseth that he had not seen the two innermost of them, yet he confides in the observations of Mon. sieur Cassini, and suspects also that there may be more yet discovered, when the glasses of 170 and 210 foot, made the most accu rate by his brother, shall come to be used for that purpose. But what to determine concerning the furniture, or nature of all these moons, though he thinks them to be much the same with that of our moon. Yet as he conceives, being not sufficiently informed by observation, that the moon has the like furniture as the earth has, he is at a stand, and knows not well what to determine concerning them. He grants we can plainly discover that the moon has moun tains and valleys, and other asperities as the earth has; but as he conceives there are no seas nor rivers, for that he thinks it more probable, that those spots which others have supposed seas, are only great plains of a darker colour, his reason is, for that there are

divers inequalities to be discovered in them the same as in other parts of its surface, and from thence he imagines there can be no rivers, and consequently no water, nor any atmosphere, or air. These are the difficulties which perplex him, which, if he could have removed, and that he could have been assured there had been water, he could have allowed it all the other privileges, and with Xenophanes, have furnished it with inhabitants, cities, &c. But as he conceives of it, he can neither allow it to have animals, no, nor plants. And yet at last he says, 'tis not improbable but that it may have plants and animals too, but they must have another sort of nourishment. Now by this censure of the moon he has passed the same upon all the other moons, to wit, the concomitants of 24 and h, which he judges to be of the same nature, and to expose the same part always towards their primary planet, as the moon does to the earth, by a phenomenon of one of the moons of ↳, the consideration of which suggested to him that the phænomena of the heavens must be to their inhabitants, if they could have any, and for all the rest gives an instance of those of the moon. Then he proceeds to consider the sun and the fixed stars, promising the mag. nificence of the solar system; this he does by words, because schemes he could not render them large enough to represent the proportionate magnitudes of the orbs to the minuteness of the plenary bodies; for the orb of Saturn would require an area of 360 foot in diameter, and that of the earth, one of 36 foot, to draw them proportionate to the globes, for the orb of the earth is 12,000 times the diameter of the earth's ball. And consequently the distance of the earth from the sun will be above 17,000 of 17,000,000 of German miles. To make the vastness of these distances the more conceivable, he computes them by the times that a cannon-bullet (supposed to pass a hundred fathom in a second of time) would spend in passing those spaces, whence he concludes it would be 25 years passing to the sun from the earth, 125 from 24, and 250 from H. Then he proceeds to consider the body of the sun, where he is nonplus'd, as about the moon; for he is not satisfied whether it be a solid, or fluid body, but he inclines to think it a fluid. Next, he knows not what to think of animals, or vegetables in it, since there can be nothing like any thing we know, by reason of the continual fire and heat, which would consume all such as we have here. He thinks therefore it might be made for the illuminating and en

livening of the parts of the other planets. And as for the fixed stars, he conceives them to be so many suns, and to be dispersed in the vast expansum of heaven, at various distances, and each of them to have a proper system, and planets moved about them. And though it be impossible for us ever to see those planets, by reason of their vast distance, yet from the analogy that is between the sun and stars, we may judge of the planetary systems about them, and of the planets themselves too, which probably are like the planetary bodies about the sun, (that is) that they have planets and animals, nay, and rational ones too, as great admirers and observers of the heavens as any on the earth. This represents to us a wonderful scheme of the prodigious vastness of the heavens; so that the distance between the earth and the sun, though of 17 millions of German miles, is almost nothing to the distance of a fixed star. And because of the difficulty in making observations for this purpose, in the common ways, he therefore proposes a new method of his own for this purpose, which he also explains, and by that one may the better conceive the vastness of the distance of one of the nearest, as for instance, from the sun; which by this way he proves to be 27,664 times the distance of the sun from the earth; and to make this distance yet more comprehensible, he makes use of the former explication, by the time that a cannonbullet moved as swift, as hath been just now explained. Wherefore multiplying 27664 by 25, he finds that a cannon-bullet, mov. ing a hundred fathom in a second, would be 700,000 years in its journey betwixt us and the fixed stars; here by the way he makes some reflections on Des Cartesa's Vortices, and explains his own sentiments concerning the present state of the universe, nor will he trouble his mind about their beginning, or how made, as knowing it to be out of the reach of human knowledge or conjecture.

Upon the whole matter you will here find the ingenious author's opinion, concerning the universe, with all the arguments for it, drawn from the most accurate observations that have been hitherto made that are pertinent thereunto. The only failure seems to some to be in his opinion concerning the moon and secondary planets. Upon which subject there may perhaps be shortly published a brief discourse of one who is of a somewhat differing sentiment.

[From the translation adopted by the Royal Society, 1699; and printed in the Phil. Trans. for the same year.]

CHAPTER VI.

ON THE NATURE AND CONSTRUCTION OF THE SUN AND FIXED STARS.

AMONG the celestial bodies, the sun is certainly the first which should attract our notice. It is a fountain of light that illuminates the world! it is the cause of that heat which maintains the productive power of nature, and makes the earth a fit habitation for man! it is the central body of the planetary system; and what renders a knowledge of its nature still more interesting to us is, that the numberless stars which compose the universe, appear, by the strictest analogy, to be similar bodies. Their innate light is so intense, that it reaches the eye of the observer from the remotest regions of space, and forcibly claims his notice. Now, if we are convinced that an inquiry into the nature and properties of the sun is highly worthy of our notice, we may also with great satisfaction reflect on the considerable progress that has already been made in our knowledge of this eminent body. It would require a long detail to enumerate all the various discoveries which have been made on this subject; I shall therefore content myself with giving only the most remarkable of them.

Sir Isaac Newton has shown that the sun, by its attractive power, retains the planets of our system in their orbits. He has also pointed out the method by which the quantity of matter it contains inay be accurately determined. Dr. Bradley has assigned the volocity of the solar light with a degree of precision exceeding our utmost expectation. Galileo, Scheiner, Hevelius, Cassini, and others, have ascertained the rotation of the sun on its axis, and determined the position of its equator. By means of the transit of Venus over the sun's disc, mathematicians have calculated its distance from the earth; its real diameter and magnitude; the density of the matter of which it is composed; and the fall of heavy bodies on its surface. From the particulars here enumerated, it is obvious that we have already a very clear idea of the vast importance, and powerful influence of the sun, on its planetary system.

And if we add to this the beneficent effects we feel on this globe from the diffusion of the solar rays; and consider that, by well traced analogies, the same effects have been proved to take place on other planets in this system; I should not wonder if we were induced to think that nothing remained to be added in order to complete our knowledge: and yet it will not be difficult to show that we are still very ignorant, at least with regard to the internal construction of the sun. The various conjectures, which have been formed on this subject, are evident marks of the uncertainty under which we have hitherto laboured.

The dark spots in the sun, for instance, have been supposed to be solid bodies revolving very near its surface. They have been conjectured to be the smoke of volcanos, or the scum floating on an ocean of fluid matter. They have also been taken for clouds. They were explained to be opaque masses, swimming in the fluid matter of the sun; dipping down occasionally. It has been supposed that a fiery liquid surrounded the sun, and that by its ebbing and flowing, the highest pats of it were occasionally uncovered, and appeared under the shape of dark spots; and that, by the return of this fiery liquid, they were again covered, and in that manner successively assumed different phases. The sun itself has been called a globe of fire, though perhaps metaphorically. The waste it would undergo by a gradual consumption, on the supposition of its being ignited, has been ingeniously calculated. And in the same point of view, its immense power of heating the bodies of such comets as draw very near to it has been assigned.

The bright spots, or faculæ, have been called clouds of light, and luminous vapours. The light of the sun itself has been supposed to be directly invisible, and not to be perceived unless by reflection; though the proofs, which are brought in support of that opinion, seem to amount to no more than what is sufficiently evident, that we cannot see when rays of light do not enter the eye. But it is time to profit by the many valuable observations that we are now in possession of. A list of successive eminent astronomers may be named, from Galileo down to the present time, who have furnished us with materials for examination.

In supporting the ideas proposed in this paper, with regard to the physical construction of the sun, I have availed myself of the labours of all these astronomers, but have been induced to this only by my