Unfortunately the savant has not been equal to the poet. And we cannot read his assertions respecting cometary astronomy without smiling at the inaccuracies and even blunders into which the author has fallen. It is a great defect, since the emotion which he designs to inspire misses its effect, as soon as the reader perceives the want of accord between the fact and the dream. But on the other hand we see that Poe has designedly neglected to employ any of the ordinary catastrophes which have been supposed likely to result from the rencontre of a comet and the earth. He calls in aid neither flood nor fire, in the ordinary sense, nor the disruption of the earth. Not even poison, nor the respiration of a poisonous matter. A simple addition, in increasing proportion of oxygen gas, and all is told. It is true that he speaks, we know not why, of a total extraction of nitrogen; we seek in vain for the scientific reason for this extraction. Nor is the final piercing sound and the explosion easier to understand. The effects are not as described, when a living creature is subjected to an increased pressure of an oxygenated atmosphere, as M. Bert's experiments have shown. But a final coup de théâtre was needed, and on this point Poe has made a sacrifice to the vulgar.

Other observations might be made; but we have already explained the nature of the laws applying to cometary movements, and the reader will not fail to detect the errors of the poet, who, were he writing at the present day, would be obliged to change the form and manner of his catastrophe. The known results of spectral analysis would no longer permit him to represent a comet as an agglomeration of oxygen. Likewise nothing proves that the matter of which a comet is composed is in a gaseous state; the nucleus on the contrary would appear to be either a solid or a liquid mass, and the atmosphere with which it is surrounded on all sides an aggregation of isolated particles.

CHAPTER XV.

SOME QUESTIONS ABOUT COMETS.

SECTION I.

ARE COMETS HABITABLE?

The inhabitants of comets as depicted in the Pluralité des Mondes of FontenelleIdeas of Lambert respecting the habitability of comets-That comets are the abode of human beings is a hypothesis incompatible with the received facts of astronomy.

AFTER NEWTON, and especially in the eighteenth century, by a not unnatural reaction of ideas from the Aristotelian doctrine of transient meteors, comets were regarded as bodies, stable and permanent as the planets; they were obedient to the same laws of movement, and differed only as regards appearance, by their nebulosities and tails. The astronomers of that time, taken up with the verification and calculation of their positions and orbits, occupied themselves little or not at all with the study of details which were purely physical, such as are now called cometary phenomena. Regarding them as spheroids, solid like the planets, and similar to them in the constituents of their nuclei, to people them with inhabitants followed in the natural sequence of ideas.

Fontenelle, who, as we know, was a believer in the theory of vortices, and who, moreover, regarded the heads and tails of comets as simple optical appearances, thus expresses himself in the Pluralité des Mondes.

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'Comets,' he observes, are planets which belong to a neighbouring vortex; they move near the boundaries of it; but this vortex, being unequally pressed upon by those that are

adjacent to it, is rounder above and flatter below, and it is the part below that concerns us. Those planets which near the summit began to move in circles did not foresee that, down below, the vortex would fail them, because it is there as it were crushed. Our comet is thus forced to enter the neighbouring vortex, and this it cannot do without a shock.' Also further on, Fontenelle observes, returning to the same point I have already told you of the shock which takes place when two vortices meet and repel each other. I believe that in this case the poor comet is rudely enough shaken and its inhabitants not less so. We deem ourselves very unfortunate when a comet appears in sight; but it is the comet itself which is very unfortunate.' 'I do not think so,' said the Marquise ; ‘it brings to us all its inhabitants in good health. Nothing is so delightful as thus to change vortices. We who never quit ours lead a life wearisome enough. If the inhabitants have sufficient knowledge to predict the time of their entrance into our world, those who have already made the voyage announce beforehand to others what they will see.' 'You will soon discover a planet which has a great ring about it, they will say perhaps,' speaking of Saturn. 'You will see another which will be followed by four little ones. Perhaps even there are people appointed to look out for new worlds as they appear in sight, and who cry immediately, A new sun! a new sun! as sailors cry, Land! land! Believe me, we have no need to pity the inhabitants of a comet.'

Lambert in his Lettres Cosmologiques (1765) devotes a chapter to the question, Are comets habitable? Guided by considerations foreign to science, and dominated by a preconceived idea that all globes must be inhabited, he seeks to discover reasons which may permit us to believe that comets, more numerous than the planets in the solar system, are habitable celestial bodies.