how-, succeeded in giving a wide berth to our dangerous neighbour, there being the margin of a whole month. In 1805, we had a much narrower escape; we then saved our distance by only three days. Fortunately the danger was not known till it was over. It was not, till afterwards, that the comet was known to be a periodic one. It can, however, be shewn from our knowledge of its orbit, that, in this generation at least, there is not only no probability, but no possibility of a collision.
Some astronomers, on the subject of comets, treat the popular mind as they would a spoiled child, by administering soothing and comforting assurances of all kinds. One of these is, that though we did go right through a comet, we would be none the worse of it. Judging from their tone, they would rather like the thing as a pleasant experiment. We would, however, require to know something about our suspicious neighbours, before venturing on such an experiment with anything like confidence. There would be little comfort in the assurance, that the tenuity of the substance is such that it would do neither good nor harm. We know that the most deadly miasmata are so subtle, that it is impossible to detect them by any chemical test, and a very homoeopathic dose of a comet, in addition to the elements of our atmosphere, might produce the most fatal effects.
It is hardly possible, at the present time, to comprehend the terror which a great comet usually in-
