SECTION I.

SUPPOSED PHYSICAL INFLUENCES OF COMETS.

The great comet of 1811; the comet wire-Prejudices and conjectures-Remarkable comets and telescopic comets -Comets are continually traversing the heavens.

IN former times when a new comet was seen to project upon the sky its vaporous star and plume of light, the first question in the mouth of everyone was, What great calamity does God announce ?

Even at the present day people may be heard enquiring what the comet signifies; but the greater number of enquirers are far more occupied with the physical effects likely to accrue, than with the supernatural import of the apparition. Do you think we shall have a warm and dry summer? is the question of some. Are we to anticipate foggy weather, heavy rains and inundations? ask others. It announces an abundant harvest, or a superior quality of the year's wine, is gladly remarked by those who have-not forgotten the comet and the good wine of the year 1811.

In a word, people readily believe that the passage of a comet within sight of the earth must be followed by certain consequences of a nature to influence not only the climate, temperature, and vegetation of the latter, but likewise the health of animals and man, for I have forgotten to say that the influence of comets upon the production of epidemics and other

maladies was formerly an article of popular belief. To give an idea of the prejudices entertained upon this subject not more than sixty years ago, we will quote from Arago the following passage taken from the Gentleman's Magazine :

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'Through the influence of the comet of 1811, the winter following was very mild; the spring was wet, the summer cool, and very little appearance of the sun ripen the produce of the earth; yet the harvest was not deficient; and some fruits not only abundant, but deliciously ripe, such as figs, melons, and wall fruit. Very few wasps appeared, and the flies became blind and disappeared early in the season. But what is very remarkable, in the metropolis and about it, was the number of females who produced twins, some had more, and a shoemaker's wife in Whitechapel produced four at one birth..."* This shows certainly an extravagant

...

imagination.

In these entirely conjectural suppositions, especially in those which are advanced in the form of questions, is there any base of truth which the astronomical science of the present day might seem at all to confirm? In the majority of cases there is every reason to believe that these assumed influences amount to nothing; but then probabilities are not certainties, and a case might arise in which the apparition of a comet could be reasonably suspected of having been concerned in the production of certain terrestrial phenomena, such as, for example, meteorological phenomena.

[* This is an extract from a letter which appeared in the Gentleman's Magazine for November, 1813 (p. 432), and is signed J. B. It has had the distinction of being quoted by Arago and by M. Guillemin; but it should be remembered that it was merely an anonymous letter, published in an unscientific periodical. It seems to me to be characteristic of a class of letters which all who are associated with astronomy frequently receive from unscientific people, rather than representative of the prejudices prevalent at the time it was written There are always persons who write letters of this kind, and sometimes, of course, they find their way into print.-ED.]

Let us examine the principal influences enumerated, and see if they are confirmed by facts; and, if not, whether there is reason to admit, of course with necessary reservations, a certain amount of probability.

influences which comets These are indisputable ;

We have already spoken of the must exercise in virtue of their mass. but, up to the present time, as we have seen, the comets of which history has made mention, and which might have been expected to produce a disturbing influence, have produced absolutely no appreciable effect. A comet passing within a short distance of the earth would in reality act upon the waters of the sea, and upon the atmosphere, for so short a time that the wave produced would be insignificant.

But may there not be comets yet unknown of masses more considerable? May there not be comets which might pass sufficiently near the earth, and remain long enough in its vicinity for their masses to occasion an appreciable disturbance? A shock or a rencontre is improbable, but possible, and, as we have seen, the consequences that would result from it are mere conjectures. As for the second question, the different velocities alone of the earth, and of any comet which might be situated for a moment in its vicinity, would, as we have already said, rapidly separate the two bodies. But this is not the kind of influence we have here to examine.

In the first place we must remember that comets are more numerous than might be supposed, that new comets make their appearance every year, that there are often several in the course of the year, and that if the influence with which they are credited belonged to them simply as comets, it would be, so to speak, continuous. This is no reason for considering it to be nil, but it is clear that it would be a very difficult matter to distinguish it from all other causes, regular or irregular. Those who have admitted, à priori so to speak, the existence

of such an influence, have scarcely attempted the task of its verification.

In former times it was to comets visible to the naked eyeno others were then known-that fatal influences were alone attributed. And at the present day it is the larger and more magnificent comets, those which make a show' in the sky, that are supposed to exert an influence upon our globe. Nor is this surprising, since the greater or less visibility of a comet is a measure of its brilliancy and size, or, what comes nearly to the same thing, of its proximity to the earth.