THE AUGUST METEORS.
jiVERY ancient tradition prevails in the mountain districts which surround Mount Pelion, that during the night of the Feast of the Transfiguration (August 6) the heavens open, andi lights, such as those which surround the altar during the solemn. festivals of the Greek Church, appear in the midst of the opening. It has been thought by Quetelet, and Humboldt considered the- opinion probable, that this tradition had its origin in the successive- apparition of several well-marked displays of the August meteors, If this be so, the date of the shower has slowly shifted,—as that of the November shower is known to have done,—until now another holiday is associated with it, and the simple peasants of Southern Europe recognize in the falling stars of August the "fiery tears of good St. Lawrence the Martyr."
It is wonderful to contemplate the change which in a few short years has come over all our views respecting these meteors. Ten years ago it was considered sufficiently daring to regard the August system as part of a zone of cosmical bodies travelling in an orbit as large perhaps as that of our own earth. Now, the distance even of Neptune seems small in comparison with that from which those bodies have come to us, which flash athwart our skies in momentary splendour, and then vanish for ever, dis- sipated into thinnest dust by the seemingly feeble resistance of our atmosphere. Accustomed to associate only such giant orbs aa Saturn and Jupiter, Uranus and Neptune, with orbits which must be measured by hundreds of millions of miles, the astronomer sees with wonder these tiny and fragile bodies traversing paths yet vaster than those of the 'outer planets. And even more remark- able, perhaps, is the immensity of the period which the August- shooting-star has occupied in circling around the central orb of our system. Each one of the bodies which will be seen next Tuesday has been in the neighbourhood of the earth's orbit many times before ; yet the last visit made by them took place years before the birth of any person now living, since the period of meteoric revolution has been proved to be upwards of 118 years.
Another strange feature of the August meteor-system is the enormous volume of the space through which, even in our neigh- bourhood, the meteor-stratum extends. .The famous November system is puny by comparison. Striking that system at a sharp angle, the earth traverses it in a few hours, so that if the earth went squarely through it the passage would occupy, it has been estimated, less than a hundred minutes. Thus the depth of the November meteor-bed has been calculated to be but a hundred thou- sand miles or so. But the earth takes nearly three days in passing through the August meteor-system, although the passage is much more direct. For the August meteors come pouring down upon our earth almost from above, insomuch that the radiant point on the heavens whence the shower seems to proceed is not very far from the North Pole ; whereas the November meteors meet the earth almost full front, as a rain-storm blown by a head-wind drifts in the face of the traveller. Thus the depth of the August system has been estimated at three millions of miles ; and this depth seems tolerably uniform, so that along the whole of that enormous range (to be counted, as we have said, by hundreds of millions of miles), through which the August ring extends, the system has a depth exceeding some four hundred times the diameter of the earth on which we live.
Yet it is probable that the whole weight of the August system, vast as are its dimensions, is infinitely less than that of many a hill upon the earth's surface. For the weight of the separate falling stars of the system has been determined (by one of the wondrously subtle applications of modern scientific processes) to be but a few ounces at the outside ; and even during the most splendid exhibition of falling stars the bodies which seem to crowd our skies are many miles apart, while under ordinary circumstances thousands of miles separate the successively appearing meteors. Indeed, it was well remarked by an eminent member of the Greenwich corps of astronomers, that the planets tell us by the steadiness of their motions that they are swayed by no such attractions as heavily loaded meteor-systems would exert. "The weight of meteor-systems must be estimated by pounds and ounces, not by tons," he remarked.
The spectroscope has taught us something of the constitution of these bodies, though they never reach the earth's surface. Pro- fessor Herschel, third in that line of astronomers which has done so much for science, has employed an August night or two in trying to find out what the August meteors are made of. With a spectroscope of ingenious device, constructed by Mr. Browning, F.R.A.S., for the special purpose of seizing the light of these swiftly moving bodies, Professor Herschel was successful in analyzing seventeen meteors. The most interesting of his results is his discovery that the yellow light of the August meteors is due to the presence of the metal sodium in combustion. This metal has a very striking and characteristic spectrum, consisting of two bright orange-yellow lines very close together ; and this double line was unmistakably recognized in the spectrum of the August meteors. To use the words of the observer, "their condition" (when rendered visible to us by their combustion) "is exactly that of a flame of gas in a Bunsen's burner, freely charged with the vapour of burning sodium ; or of the flame of a spirit lamp newly trimmed, and largely dosed with a supply of moistened salt."
It is strange to consider what becomes of all the sodium thus dispersed throughout the upper regions of air. There can be no doubt that in some form or other—mixed or in combination—it reaches the earth. The very air we breathe must at all times con- tain, in however minute a proportion, the comical dust thus brought to us from out the interplanetary spaces. Nay, for aught we know, purposes of the utmost importance in the economy of our earth, and affecting largely the welfare of the creatures which subsist upon its surface, may be subserved by this continual down- pour of meteoric matter. We know already that the different meteor-systems are differently constituted. For instance, the white November stars are much less rich in sodium than the yellow August ones. Each system, doubtless, has its special constitution, and thus the air we breathe is continually being dosed with different forms of metallic dust,—now one metal, now another, being added, with results in which, did we but know it, we are doubtless largely inter- ested. Nor is it certain that deleterious results do not occasionally flow from an overdose of some of the elements contained in meteors. It might be plausibly maintained, on evidence drawn from known facts and dates, that occasionally a meteoric system has brought plague and pestilence with it. The "sweating sickness" even has been associated (though, we admit, not very satisfactorily) with the 33-year returns of great displays of November shooting stars.
Without insisting on such hypotheses as these, which scarcely rest on stronger evidence than the notion that the destruction of Sodom and Gomorrah was brought about by an unusually heavy downfall of sodium-laden (that is, salt-laden) meteors, we may content ourselves by pointing out that the labours of eminent chemists have shown that the air is actually loaded at times with precisely such forms of metallic dust as the theories of astronomers respecting meteors would lead us to look for.
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