wilder than that which gives the sun its heat by a constant shower of meteors, the arrest of whose motion supplies the heat lost by the sun by constant radiation; or the opposition theory, which, instead of pelting the sun with meteors, accounts for these meteors as masses of vapour escaping from the bubbling, boiling surface of the sun, and projected with such velocity as to reach the earth after condensation by the extreme cold of planetary space.

The CHAIRMAN.-I am sure you will allow me to return thanks to Mr. Mitchell for this very interesting and instructive paper. In this age there is so great a tendency to attach so much to authority, that it is very valuable to see how very little authority is sometimes worth, and how great is our ignorance and how little our knowledge of that which we profess to know very well. We shall be glad to hear any gentleman who has any remarks to add or suggestions to offer.

Mr. REDDIE. I think the paper that we have heard this evening (which I am sure we have all listened to with much pleasure) is one that scarcely admits of discussion. That is one of the disadvantages of having very good papers. We had Professor Kirk's paper at our penultimate meeting, and Mr. Mitchell's paper to-night, both giving us such able discourses on the subjects they treat of, that there is nothing left for us to say. (Hear, hear.) Mr. Mitchell will complete his paper for our Journal of Transactions, I beg leave to say, although the latter part of it was delivered extempore. With reference to some of his remarks, I should be very glad if he could collect some of the various reports respecting the recent meteoric shower as seen at different places. I think they would demonstrate the truth of what he has said as regards the uncertainty there must be as to the real heights of those bodies; for the accounts have varied so much that either the witnesses must have stated very incorectly what they saw, or else they did not all see the same things. If you will take the accounts published in London and different parts of England, and others at Malta, you will observe that both as to the numbers of the falling stars, and in various other particulars, they do not agree with one another. And I think it will yet prove that most probably this is an electrical phenomenon, in which there are brilliant scintillations, all more or less tending in one direction. But there is certainly a great discrepancy as to the quantity of those observed; and I may say even as to their apparent distances from the earth. Even in this country I observe in the various accounts in The Times there was a great difference as regards the number of the meteors; and even people in the same house, describing what they saw, gave different accounts to one another the next morning. I think it is almost impossible to consider that those majestic slow-moving fire-balls (one of which I saw two years ago, in November, the only one I have ever seen in my life, it was about the size of the moon, and moved in a southwesterly direction,) can be considered similar either to those heavy masses of meteoric matter, or to those mere scintillations called falling stars. You

might just as well consider them as actually falling stars, because they are like the stars in heaven; for although we call them falling stars, we know they have nothing in common with stars. I am sure Mr. Mitchell's account will be a most valuable record on the subject in our Transactions, and it will very likely complete No. 4 of our Journal.

Professor OLIVER BYRNE.-I have a few remarks to offer to you, and they are based upon demonstration, and not conjecture. I am going to base what I have to say upon what Archimedes based his mechanics. It is, "the law of sufficient reason," carried out by Leibnitz, and made great use of by Laplace. It is known to all philosophers, who make use of it to prove one thing, but reject it when you want to prove another. Leibnitz made great use of it, and I should have said that our very learned and worthy VicePresident has brought before us a subject that requires our most serious consideration, because it is the only index we have left, it is really the only weather-vane by which men can discover the motions of the heavens. Now, I have taken 13 of the principal stars, and I have calculated their positions up to the 1st January, 1867, and their proper motions and declinations. It was a great deal of labour, and I am sure that each of these stars loses place, as regards the observer, by 600 or 700 yards. The pole star and others have travelled 666 yards out of their places. These stars all move, and there is a delusion in astronomers about them; they all say they have a proper motion, and it is a curious thing that all the negative quantities of these 13 great stars differ but 16" from all the positive motions of the larger stars in the heavens

The CHAIRMAN.-The difference between the positive and the negative quantities.

Professor BYRNE.-This motion takes place, which I am going to prove by the law of sufficient reason. No philosopher has ever been able to prove the parallelogram of forces; and all attempts to prove have failed when the quantities compared are incommensurable. If these had relations to one another, we could get a law, but it is impossible. If you give me the diagonal of the square, no one can tell the length of the side-the diagonal may be 20 feet, but you cannot tell the length of the side-that seems simple, yet it is impossible that any one can find it out. The diameter of a circle may be

10 feet, no one can tell the circumference. There is no law for the incommensurability of quantities, and the law of sufficient reason will not apply. What I am going to prove will be proved with the exception that I am not taking incommensurable quantities, and the only specimen of human reasoning totally perfect is the 5th Book of Euclid, because it takes in the doctrine of incommensurable quantities altogether; and consequently what I am going to say is subject, not to comparison with incommensurable quantities, but quantities that can be measured by practice. I suppose I have taken the right motion of the stars; but to show I have not done so, my empirical rule differs 16 seconds, which is very small. We will take 13 of the larger stars, and each one in its turn operates upon its neighbour. The question is this, the conclusion I am coming to, the object I wish to prove is this,—and

I wish to prove it in this way, that the actions of the forces of these stars act on one another. If I take hold of this book, and Mr. Mitchell attempts to pull it at an angle to me, and I pull it at the same angle, there is no reason why the book will fall to him or to me, if both pull at the same angle with the same strength. It will remain in the position in which it is, and consequently obey neither one nor the other. There can be no action in the matter, and there can be no motion in the stars unless some force is operating in favour of one rather than the other. When a man tells me that this meteoric stone came down on the ground with a certain velocity, it depends on the short time in which it stopped; it is not in the velocity, the force depends on the shortness of the time. (Question.) This may be very awkward; I will try and do my best, because Mr. Mitchell's paper bore on the velocity and force of the aerolites falling on the earth. I returned from the subject to the equal pulling of the proper motion of the fixed stars, showing the balancing of one another (which I did not like to read one by one), not all going one way, but balancing one another. There is no system of the law of gravitation whatever, it is a secondary thing compared with the actions of the stars on one another

Mr. REDDIE. You began with the fixed stars, and then you passed from them to the planets; but the difficulty is to understand how you mean to connect them together and with the subject of meteors.

The CHAIRMAN.-Keep to the question.

Professor BYRNE.-Am I in order? I am afraid I wish to carry the thing one way too far; but to go back to the force of a body and the blow it gives, as an aërolite coming any distance; does that depend upon the impression so much as the space of the time in which the body comes. My whole object in rising is this, to show that there is an action in the fixed stars, upon which the force of gravitation is secondary—

Mr. REDDIE.-I do not think this question of the fixed stars has anything to do with meteors.

Professor BYRNE.-I got up to show that it had. Mr. Chairman, I submit I got up to show that. Perhaps Mr. Reddie will show me that it had not,

and I will then sit down.

Mr. REDDIE.-It is not for me to do so. I should be sorry to interrupt unnecessarily any gentleman when speaking, but now I must throw myself on the good-nature of the meeting. I must say, that I do not see that Mr. Byrne has shown that there is any connection between the fixed stars and meteors; and I do think it irregular to go into such elaborate questions as he has entered upon, when we have a specific subject before us. If, however, the other question is to be gone into, I think we ought to have it treated a little more coherently; and if Professor Byrne will write a paper on the motions of the fixed stars, which it appears to me is a totally distinct subject, I am sure we shall all be most glad to hear him. Professor Byrne is a great mathematician, and is entitled to bring those things forward; but we must keep to one subject at a time; and I certainly do not understand how these remarks of Professor Byrne can be considered as having any reference to the

paper of Mr. Mitchell, if Mr. Byrne will excuse me for saying so. He knows I am a sincere friend of his, and that I should be glad to hear him upon any point connected with astronomy, but pray let us have it at the proper time and place. (Hear, hear.)

Mr. WARINGTON.-I should like to ask one question of Mr. Mitchell. I never before heard the theory started, which seems a probable one, that the origin of the shooting stars is electrical rather than cosmical. And I would ask, whether there is anything in the phenomena of the aurora borealis similarly periodical, as to particular seasons or days of the year, with the periodical display of meteors? Because, if there is any such periodicity here also, it would very materially help out the hypothesis. I am not aware whether there is anything of the kind, and perhaps Mr. Mitchell will tell us.

The Rev. WALTER MITCHELL.-In reply to Mr. Warington, I may state that I am unacquainted with any period days marking a great display of aurora borealis. I only wished to point out several analogies between the two phenomena. In some latitudes the aurora is almost nightly visible, like the display of falling stars in other latitudes. Then there is something similar in the intermission of the brilliant displays of both phenomena-the aurora appearing in lower latitudes for a few years, and then disappearing altogether, like the maxima exhibition of falling stars. With regard to the period days of falling stars, I may state that these are not the only meteoric phenomena (using the term meteor in its widest sense), which are periodic. There are certain latitudes where the return of the monsoons and the change of the trade winds occur with such regularity as to allow their prediction nearly to a day. In defence of the theory first put forth by Soldani as to the terrestrial origin of meteorites, I think many facts might be urged, though I doubt whether they would be considered sufficient to demonstrate its truth. The majority of meteorites are admitted to be identical in composition with solid masses ejected from our own volcanoes. These masses, for aught we know, might have been projected in a state of vapour, and might remain for some time uncondensed in our upper atmosphere. Or, if condensed, they might remain, as Professor Shepherd has stated, in minute subdivision till condensed into a solid mass by some such known agency as electricity. We know that some metals do evaporate like water, and their vapour ascends like that of water into the atmosphere; mercury is an instance. We are ignorant, because our analysis is not sufficiently sensitive to tell us, how many of the constituents of meteorites may be diffused through our atmosphere. If not in a state of vapour, yet in a state of minute subdivision, such constituents could be carried by the upper trade winds thousands of miles. Vessels on the Mediterranean and in the Atlantic sometimes pass through a red fog for days together. A red dust may be collected on the rigging of ships, and Professor Ehrenberg has shown that this dust is composed for the most part of the shells of foraminiferæ, which have been wafted thousands of miles from the plains of South America by the upper trade winds. These fogs, covering as they do some hundreds of square miles, must contain many tons of material

thus wafted by the winds. Under certain meteoric conditions, this minutely subdivided matter returns again to the earth. Just as, in ordinary conditions of the atmosphere, the moisture descends to the earth as rain or snow, we know that under certain more extraordinary conditions, large masses of ice are formed, supported during that formation contrary to the laws of gravity, and then hurled to the earth. There appears some analogy between this latter phenomenon and that of the formation of a meteorite. The peculiar noise, like a discharge of small arms, which heralds the fall of a meteorite from a cloud, in a somewhat modified form, accompanies the formation of blocks of ice in the air. We know, as in the beautiful test for arsenic discovered by Marsh, that a solid metal arsenic may be combined with an invisible gas, hydrogen, and form together an invisible gas. When this is combined with oxygen, a spark of electricity is sufficient to combine the oxygen and hydrogen into water, and precipitate the arsenic in a pure metallic state. May there not be some analogy between this fact and the formation of meteoric iron? I may add, as it appears to militate against the electrical origin of falling star storms, that I have ascertained that no disturbance was observed in the delicate magnetic needles of Greenwich Observatory during the late November display. On the other hand, I believe that it is recorded that the most delicate electrometers have not been in the slightest degree affected during a magnificent display of aurora borealis.

The Rev. Dr. IRONS.-I think Mr. Warington's point was this. There is admitted to be a certain monent of periodicity respecting the wonderful displays of the meteors called falling stars, and we know that the last shower was predicted. Could you affirm anything about displays of the aurora borealis being predicted? because, if not, it would seem hard to connect the two things together-the one being predictable, and the other casual.

The Rev. WALTER MITCHELL.-I may say in reply to this question that I do not know of any display of aurora borealis being predicted with the same degree of precision as to any particular day as these exhibitions of falling stars, but I have called attention to the fact that the maximum appearance on any day does not follow any period of years; that for a number of years in succession so few stars have been seen to fall on the 13th or 14th of November, or from the 10th to the 12th of August; that certain of the French observers, one of whom devoted attention night after night to counting them, gave up altogether the theory of periodicity. I might perhaps say that the prediction of the meteoric display of 1866 was a philosophical "fluke "—it was a fair guess from probabilities founded upon the years 1766, 1799, 1833. It was a good guess to say 1866; but, as I have before pointed out, there have been displays between those years which have not and could not have been predicted; that of 1766 was included by mistake; nor can we predict whether in November, 1867, we shall have a more abundant shower of falling stars than we had last year, or in 1864 or 1865.

The CHAIRMAN.-I quite agree with Mr. Mitchell that there is no periodicity with regard to meteoric showers, for I have been a great deal in tropical latitudes, where falling stars are constantly seen night after night,