near the earth of a meteoric trail traveling in the track of the comet. When the question of a possible collision was mooted in 1832, Sir John Herschel remarked that such an occurrence might not be unattended with danger, and that on account of the intersection of the orbits of the earth and the comet a rencontre would in all likelihood take place within the lapse of some millions of years. As a matter of fact the collision did take place on November 27, 1872, and the result, so far as the earth was concerned, was a magnificent display of aërial fireworks! But a more telling piece of ready-witted sagacity than this prompt employment of the telegraph for the apprehension of the nimble delinquent can scarcely be conceived. The sudden brush of the comet's tail, the instantaneous telegram to the opposite side of the world, and the glimpse thence of the vagrant luminary as it was just whisking itself off into space toward the star Theta Centauri, together constitute a passage that stands quite without a parallel in the experience of science." But did the earth escape with a mere shower of fireworks? I have argued that the material of a comet consists of a solid nucleus, giving out fire and gas, enveloped in a great gaseous mass, and a tail made up of stones, possibly gradually diminishing in size as they recede from the nucleus, until the after-part of it is composed of fine dust ground from the pebbles and bowlders; while beyond this there may be a still further prolongation into gaseous matter. Now, we have seen that Biela's comets lost their tails. What became of them? There is no evidence to show whether they lost them in 1852, 1859, 1866, or 1872. The probabilities are that the demoralization took place before 1852, as otherwise the comets would have been seen, tails and all, in that and subsequent years. It is true that the earth came near enough in 1872 to attract some of the wandering gravel-stones toward itself, and that they fell, {p. 413} blazing and consuming themselves with the friction of our atmosphere, and reached the surface of our planet, if at all, as cosmic dust. But where were the rest of the assets of these bankrupt comets? They were probably scattered around in space, _disjecta membra_, floating hither and thither, in one place a stream of stones, in another a volume of gas; while the two heads had fled away, like the fugitive presidents of a couple of broken banks, to the Canadian refuge of "_Theta Centauri_"--shorn of their splendors and reduced to first principles. Did anything out of the usual order occur on the face of the earth about this time? Yes. In the year 1871, on Sunday, the 8th of October, at half past nine o'clock in the evening, events occurred which attracted the attention of the whole world, which caused the death of hundreds of human beings, and the destruction of millions of property, and which involved three different States of the Union in the wildest alarm and terror.