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zadrant. By proposes to of the radius, ces, since the
to the author of this article, to have made one supposition the foundation of another, and that of others, in order to attain probability, which is the utmost we can expect, when we are reasoning upon
bodies too remote for even an apparent diameter.
Mr. Mitchell observes,
'The very great number of stars that have been discovered to be double, triple, &c. particularly by Mr. Herschel, if we apply the do&rine of chances, as I have heretofore done in my "Enquiry into the probable Parallax, of the Fixed Stars," published in the Philosophical Transactions for the year, 1767) cannot leave a doubt with any one, who is properly aware of the force of those arguments, that by far the greatest part, if not all of them, are systems of stars lo near to each other, as probably to be liable to be affected fenfibly by their mutuat gravitation; and it is therefore not unlikely, that the periods of the revolutions of some of these about their principals (the smaller ones being, upon this hypothesis, to be considered as satellites to the others) may some time or other be discovered.'.
It was neceffary to quote this passage particularly, fince it is the first time we recollect any of the fixed stars to have been considered as satellites. The author is fufficiently aware of the length of time requisite either to confute or establish this idea,
He proposes to measure the distance, density, and magnitude of thefe bodies by the diminution of the velocity of light, if fight be under the laws of gravitation. We ihall select his own words.
• The diminution of the velocity of light, in case it hould be found to take place in any of the fixed stars, is the principal phænomenon whence it is proposed to discover their distance, &c. Now the means by which we may find what this diminution amounts to, seems to be supplied by the difference which would be occasioned in consequence of it, in the refrangibility of the light, whose velocity should be fo diminished. For let us--Suppose with fir Isaac Newton (see his Optics, prop. vi. par. 4 and 5.) that the refraction of light is occafioned by a certain force impelling it towards the refracting medium, an hypothesis which perfe&tly accounts for all the appearances. Upon this hypothesis the velocity of light in any medium, in whatever direction it falls upon it, will always bear a given ratio to the velocity it had before it fell upon it; and the fines of incidence and refraction will, in consequence of this, bear the same ratio to each other with these velocities inversely. Thus, according to this hypothesis, if the fines of the angles of incidence and refraction, when light passes out of air into: glass, are in the ratio of 31 to 20, the velocity of light in the glass must be to its velocity in air in the same proportion of.
31 to 20. But because the areas representing the forces genefating these velocities, are as the squares of the velocities, these areas must be to each other as 961 to 400. And if 400 reprefents the area which corresponds to the force producing the original velocity of light, 561, the difference between 961 and 400, must represent the area correfponding to the additional force, by which the light was accelerated at the surface of the glass.'
Mr. Mitchell imagines also, that a prism, with a small refracting angle, would be a convenient instrument to measure the difference of the velocity of light. We are surprised that he has not himself tried the experiment, as the instrument is so easily procured. The whole paper is ingenious, and will probably be found to deserve attention.
Art. VIII. A Meteorological Journal for the Year 1782, kept at Minehead, in Somersethire. By Mr. John Atkins.-Meteorological journals are of considerable utility, when con. nected with the prevailing epidemics; but, independent of them, are solitary detached facts of curiolity rather than advantage. This diary is, in our opinion, unneceffarily minute ; and from the sudden changes in the thermometer, we strongly suspect that this inftrument is affected by the reflection of the fun, though not exposed to its direct beams. Few are aware by what inconsiderable causes a nice thermometer is influenced. The rain, during the year, at Minehead, was in 1782, 31.26 inches; and this quantity is seldom exceeded, even in the situations most subject to rain.
Art. IX. Description of a Meteor, observed August 18, 1783, By- Mr. Tiberius Cavallo, F.R.S.- Art. X. An Ac. count of the Meteors of the 38th of Auguit and 4th of O&ober, 1783. By Alex. Aubert, Esq. F. R.S.- Art. XI, Ob. servations on a remarkable Meteor seen on the 18th of August, 1783. By William Cooper, D. D. F. R. S. Archdeacon of York.Art. XII. An Account of the Meteor of the 18th of August, 1783. By Richard Lovell Edgeworth, Esq. F.R.S.
Art. XVIII. An Account of some late fiery Meteors ; with Observations. By Charles Blagden, M. D. Sec. R. S.We join these different articles, as they relate to the same or similar phænomena; but shall give a particular account of Dr. Bladgen's observations, fince they comprise those of the former articles, as well as many other descriptions of the same meteors. The first occurred the 18th of August, about 26 minutes after 9. It seems to have arisen somewhere in the northern ocean, beyond the extremities of this island, and was observed in the N. N. W. quarter, from whence it proceeded 8. S. Es almot in the direction of the magnetic meridian.
When forces gene.
. 400 repre.
ing the ori en 961 and ; additional face of the
When it was nearly over Lincolnshire, it seemed to deviate, in its course, more towards the east; and this deviation was marked by two loud reports, described by Dr. Cooper near Stockton, each as equal to that of a nine-pounder, and pretty distinctly heard at Windsor, by Mr. Cavallo. At this time too, the ball seemed to burst into many smaller ones; but soon resuming its original course and appearance, passed the Straits of Dover, and was probably seen as far as Rome, It seems to have extended its course above one thousand miles, and not to have been less than fifty-five miles above the surface of the carth : its transverse diameter was probably near half a mile;' and its real elongation behind, for the apparent length of train was delusive, seems seldom to have exceeded twice or thrice its real transverse diameter: its velocity was aftonishing, for it probably exceeded twenty miles in a second.
This is a short account of the result of various obferva. tions; we are obliged to omit Dr. Blagden's reasoning, but
are satisfied that his computations are within the truth. The second meteor appeared the 4th of O&tober, at 43' past 6 in the evening. Its direction was nearly the same as that of the first, and the height seems not to have been lefs; but its duration was fo tranfitory, that few obfervations were made
ven in the
Dr. Blagden then proceeds to some general remarks on the nature of these surprising bodies, which seem almost to realise Buffon's visionary system, of pieces ftruck from the sun, whirled with endless violence o'er the pendant world,' till, their projectile force diminishing, they yield to the attractive power of some other fun, and become sober planets, and new worlds. But many will think, with our author, that this fanciful hypothefis scarcely deserves attention. Dr. Blagden has not even condescended to mention it in his enumeration of the different opinions relating to the cause of these or similar meteors. He is inclined to think them of an electrical nature ; or perhaps, an accumulated light, of the same kind with that which darts and plays in the aurora borealis. The hilling noise, which some observers describe, when the meteor pasies near them, is felt in northern countries on the appearance of these lights ; and their direction in the magnetical meridian supports the analogy. We shall extract the following quotation from professor Gmelin, on account of its curiosity, though we think, with Dr. Blagden, that the appearances are exagge rated,
“These northern lights begin with single bright pillars, rifing in the N. and almost at the same time in the N.. E. which gradually increasing, comprehends a large space of the heavens, M3
yush about from place to place with incredible velocity, and finally almost cover the whole sky up to the zenith. The streams are then seen meeting together in the zenith, and produce an appearance as if a vait tent was expanded in the heavens, glita tering with gold, rubies, and fapphire. A more beautiful spectacle cannot be painted; but whoever Mould see such a northern light for the first time, could not behold it without terror. , For however fine the illumination might be, it is at. tended, as I have learned from the relation of many perfons, with such a hissing, cracking, and rushing noise throughout the air, as if the largest fire-works were playing off. To describe what they then hear, they make use of the expression spolocbi chodjat, that is, the raging host is passing. The hunters who pursue the white and blue foxes in the confines of the Icy sea, are often overtaken in their course by these northern lights. Their dogs are then so much frightened, that they will not move, but lie obstinately on the ground till the noise has passed. Commonly clear and calm weather follows this kind of northern lights. I have heard this account, not from one person only, hut confirmed by the uniform testimony of many, who have spent part of several years in these very northern regions, and inhabited different countries from the Yenisei to the Lena; so that no doubt of its truth can remain. This seems indeed to be the real birth-place of the aurora borealis."
Our author does not imagine that the meteor's direction is influenced by magnetism ; but that the direction of the magnetic power is produced by the accumulation of the electric fluid, in the N. N. W. quarter. This is indeed the center of the aurora borealis ; for, though we have seen it in many disferent quarters, yet it scarcely ever appears in the S. S. E. We have seen every point of the compass illuminated at one time, except this ; and we have never seen it enlightened at the same time with the North. Those will understand this variety, who attend to the different states of positive and negative electricity; or who recolle&, that some meteors proceed from the south, though they still continue in the magnetic meridian.
Art. XVII. On a Method of describing the relative Position and Magnitudes of the Fixed Stars ; together with some Aftronomical Observations. By the Rev. Francis Wollaston, LL. B. F. R. S.-As so many changes have occurred in the appearances of the fixed stars, Mr. Wollaston proposes, that altronomers should examine their present appearance with accuracy, and form a more exact celestial aulas than has yet been published. To a night-glass of Dolland's construction, which magnifies about fix times, and takes in as many degrees of a great circle, Mr. Wollaston has added four wires, crossing each other in the centre. By this means any Itar may be brought
LXXIV. Part I. Encredible velocity, and the zenith. The streams,
zenith, and produce an Hed in the heavens, glita ire. A more beautiful pever should see such a Id not behold it without tion might be, it is atlation of many perfons, ng noise throughout the aying off. To describe of the exprefiion spoloebi ing. The hunters who confines of the Icy sea,
these northern lights. ed, that they will not till the noise has passed. vs this kind of northern from one person only,
to the centre, and the relative tituation of the surrounding ones easily sketched on a card, and their places are afterwards to be reduced to the general atlas. If the situation of any ftar is doubtful, it may be brought to the centre, and its place more exactly ascertained. After the principal Itars are thus marked, the plan may be filled up by afing glaffes of a greater power, and fixing the situation of smaller stars: the whole atlas may, in Mr. Wollalton's opinion, be 'foon completed, if aftronomers will divide the heavens into particular districts, and each confine himself to one. The paper is concluded with an account of different astronomical observations.
The only remaining articles of this volume relate to Mr. Cavendish's experiments on air, and the controverfy which they have occasioned between him and Mr. Kirwan ; but, as we wish to examine the subject with care, we must delay our account of it till the appearance of our next Number.
y of many, who have
This seems indeed to
will understand this
A System of Surgery. By Benjamin Bell, Member of the Royal
College of Surgeons, one of ihe Surgeons to the Royal Infirmary, and Fellow of the Royal Society of Edinburgh. Illustrated with Copper-plates. Vol. III. 8vo. 65. in Boards. Ro
binson. IN N the Fifty-fifth and Fifty-seventh Volumes we have care.
fully examined the former parts of this work, and, on that account, may be now more concise. The third volume contains the chirurgical treatment of affections of the brain from violence, and diseases of the eye. It is distinguished by the fame clearness and accuracy which we have already mentioned, and it is extended with the same minuteness : a minuteners which may be necessary to young practitioners, and on subjects of importance, but which is feldom agreeable to proficients.
In trepanning, Mr. Bell recommends the trepan, in preference to the trephine. He disapproves of removing a large portion of the scalp, but advises the practitioner to raise it in the usual manner; and, if necessary, to 'cut off the corners.' We look on it as a material improvement in modern practice, that every portion of the scalp, except what may be injured by the contufion, is preserved and united by the first intention. Mr. Bell's fagacity has discovered the utility of this method in general; and we now only plead in favour of the little angles. Our author thinks that a contra-fissure may easily occur, and that even the internal table may be fractured, while no fracture appears on the external surface. A shock will certaiply sometimes break a more thin brittle substance, when
the relative Pofition
has yet been pub-
many degrees of a wires, crofing each 28 may be brought