earth, since, during the eight hours, while the meteoric shower lasted, (and perhaps it lasted much longer,) the earth moved in its orbit through the space of nearly 550,000 miles.

We have seen that the meteors appeared to be analogous, in their constitution, to the material of which the nebulous matter of comets is composed, in all the particulars in which we can compare the two.. We may be permitted, therefore, in order to avoid circumlocution, to call the body which afforded the meteoric shower, a comet, while we pursue the inquiry, whether it exhibited the other attributes of that class of bodies.

The leading circumstances to be accounted for are the following: Why the phenomenon remained so long stationary with respect to the earth? Why it was seen in that particular part of the heavens? Why it returns at stated periods, having appeared at Mocha, in Arabia, just one year preceding, and, in a manner very similar to the present, as described by Humboldt, and by Ellicot, thirty-four years before?

Let 8, &c. (fig. 5.) represent the plane of the ecliptic, with

the twelve signs, AEB the earth's orbit, S the sun, and E the earth. On the morning of Nov. 13th, the place of the sun was in 211° of Scorpio, and that of the comet in 2330 of Leo, (as observed at New Haven) being distant from the sun within 210 of three signs or 90 degrees. The line of direction, therefore, as seen from the earth, was very nearly a tangent to the earth's orbit, and consequently coincided nearly with the line of direction in which the earth itself was moving. In other words, the earth was moving almost directly towards the comet. Therefore, S' being the place of the sun among the signs, E' that of the earth, and C' that of the comet, join EC', and the comet's place will be in the line EC',* and, as was before shown, very near to E. Let it be at C.

Now the comet remained apparently at rest, and of course near the line EC' for at least two hours. This it could not have done, unless it had been moving in nearly the same direction as the earth, and with nearly the same angular velocity around the sun. For had it been at rest, the earth, moving at the rate of 19 miles per second, would have overtaken it in less than two minutes; or, had it been moving in the opposite direction, the meeting would have occurred in still less time; or had not the angular velocities of the two bodies been nearly equal, they could not have remained so long stationary with respect to each other. Hence we conclude, (1.) that the body was pursuing its way along with the earth around the sun.

Taking it for granted that the orbit of the body is elliptical, like the orbits of all the other bodies of the system, we infer that, at the time of observation, it must have been either at its perihelion, or its aphelion, otherwise its angular velocity could not have corresponded so nearly to that of the earth. The regular return of the phenomenon, at short periods, indicates that the aphelion, and not the perihelion, is near the orbit of the earth. Another reason will be stated hereafter, which, it is supposed, confirms this conclusion. As the body was very near the earth at the time of observation, it must have been at its aphelion; and being seen then, only 710 from the ecliptic, the plane of its orbit must be inclined at a small angle to the plane of the ecliptic, so that the body itself, if seen at all, will be seen within the zodiac. From all these considerations we conclude, (2.) that the body revolves around the sun in an elliptical orbit, but little inclined to the

* 73° northward of the plane of the ecliptic, as observed at New Haven.

plane of the ecliptic, and having its aphelion near to the orbit of the earth.

Let us inquire, next, what is the periodical time? Since the same phenomenon was exhibited at Mocha, on the morning of the 13th November, 1832, and on a much larger scale than that, in various parts of the world, on the morning of the 12th November, 1799, we cannot suppose such a coincidence in the time of the year to have been purely accidental, but must conclude that the periodical time of the comet, and that of the earth, bear to each other a ratio which can be expressed in whole numbers; so that after a certain number of revolutions of the two bodies, corresponding to the terms that express their ratio, they will come together again. They could not come together, as they did, on two successive years, unless the periodical time of the comet was nearly an aliquot part of that of the earth, such as one half, one third, &c. Now, if the time be any aliquot part of a year, it must be one half, so that the comet would perform two revolutions, while the earth performs one; for, were its period only one third of a year, the line of the apsides would not be long enough to reach the earth. This will be obvious from the following estimate. Let D represent the axis major of the earth, and d that of the comet's orbit, their times being as 3 to 1. Then, by Kepler's

Taking D=190,000,000 miles, d=91,343,000 for the whole major axis, which is not equal to the distance from the sun to the earth. But, supposing the times as 2 to 1, we have

22:12::D3 d3, whence d=119,692,000 miles; giving for the perihelion distance 24,692,000, and for the aphelion 95,000,000 miles. Hence we conclude, (3.) that the body has a period of nearly six months, and its perihelion a little below the orbit of Mercury.

The transverse axis and the foci being determined, the ellipse may be described. Therefore, join CS, and produce the line CS to D, making SD equal to the perihelion distance, and upon CD describe the ellipse CFD, and it will represent the orbit of the comet.

This is to be regarded only as a first approximation to the true periodic time. The distance from the sun, instead of being taken, as here, at the extremity of the body, ought to be reckoned from the center of gravity, if we knew where to fix that. Nor can we suppose that the periodical time is very uniform, since a light nebulous body like the one in question, crossing as it does the orbits of Venus and Mercury, and having its perihelion near the orbit of the latter,

would be subject to very great perturbations, sufficient to alter the dimensions of its orbit at every revolution. It might, for example, by coming into near conjunction with Mercury, have its periodic time greatly shortened, and be compelled, for a long period, to revolve nearer to that planet than it does at present; and again by coming into a similar position with respect to the Earth, its orbit might be enlarged, and its periodic time increased, so that it might for a long period revolve nearer to the earth than before. I am not able at present to assign the amount of these disturbing forces, but it is easy to see that they exist, and must greatly influence the motions of the body.

The reader will very naturally suppose that, if a comet had approached so near to the earth, having the plane of its orbit in the zodiac, it would have been visible, first on one side of the sun, and then on the other, like an inferior planet. There are grounds for believing that such is the fact, and that a body answering to the conditions of the supposed comet, has been seen, at intervals, ever since the 13th of November, and is still (March 31st) visible in the west after sunset.

By inspecting figure 5, it will be seen, that at the time of the meteoric shower, the body must have been westward of the sun, and if visible at all, must have been seen in the east before sunrise; that in consequence of the greater velocity of the earth,* the comet would almost immediately afterwards be in such a position with respect to the earth, as to appear very near the sun, and shortly would be seen to the eastward of that luminary, and set after him; and it would either move onwards before the sun, or backwards so as to disappear from the evening sky, according to the relative positions of the comet, the earth, and the sun. It will be farther manifest, on a little reflection, that a nebulous body of considerable extent, when brought very near to the earth, would cover a large space in the heavens. If, for example, the body were a comet of an elongated figure, as is usual in those bodies, it might, in certain positions, cover an immense arc in the sky, extending from the meridian to the horizon, or even much farther. We will endeavor shortly to make this matter plain by a diagram. Let us now see if we have any evidence of a body like the

At the aphelion, the velocity of the body is determined as follows: (semi axis major): (Per. dist.) :: Velocity in the cir. : Velocity in the ellipse. That is, 18.92 miles per second being the mean velocity of the earth, (59.846): (24.692): 18.92: 12.15.

one supposed, having been seen in various positions, corresponding to those which a comet, revolving after the manner inferred in the foregoing paragraphs, must have assumed.

1. Such a luminous appearance was exhibited on the morning of November 13th, being seen in the east before the dawn of day.

Thus Mr. Palmer* says that "an auroral light, resembling day break, appeared constantly in the east from the time when his observations commenced," [2 o'clock, A.M.] Mr. P. stated to the writer, that this light was so bright, and so much resembled the morning dawn, that a member of his family got his pail to milk the cows, supposing it to be day break, but found it was only 4 o'clock.

Mr. Darius Lapham (p. 378) says, that at Cincinnati, "an aurora or boreal light, was seen during the meteoric shower, a little north of east. The lower edge of this bank of light appeared to be several degrees above the horizon."

Various other observers speak of seeing "an auroral light," or "an aurora borealis," but do not mention the points of compass. The greater number, however, of those who viewed the phenomenon, did not commence their observations till near day break; and others were too much occupied with the falling meteors, to notice such a light, although visible in the east. The writer quoted from in the Boston Centinel, (p. 367,) says, "there was a vapor in the atmosphere, visible round the horizon, which in the south east assumed a very beautiful appearance during ten minutes, about half an hour before sun rise."

2. A peculiar light was seen eastward of the sun, visible in the west after sun set, as early as the first of December.

I beg leave to repeat what was said on this subject in the former part of this article, p. 398. "The writer of this article observed an appearance resembling zodiacal light, between the hours of 7 and 8, on the evenings of Dec. 1st and 3d. It consisted of an auroral appearance in the west following twilight, being an apparent prolongation of the latter. It reached to a length of about 25 degrees, towards the head of Aquarius." Also on page 410, "The same appearance has been exhibited as late as Dec. 29th, in a form much more imposing than on either of the preceding occasions. It was observed immediately after twilight, being brighter than the zodiacal light, not len

* See the last No. of the Journal, p. 384.