Dr. Huggins, in a rather disappointing article on comets, recently communicated to a contemporary, remarks that the nucleus, though an apparently insignificant speck, “is truly the heart and kernel of the whole thing—potentially it is the comet.” This has scarcely yet been proved, though it appears exceedingly probable. It is true, however, as he adds, that this part only of the comet conforms rigorously to the laws of gravitation, and moves strictly in its orbit. “If we could see a great comet,” he proceeds, “during its distant wandering, when it has put off the gala trappings of perihelion excitement, it would appear as a very sober object, and consist of little more than nucleus alone.” This again seems probable, though it has never yet been proved, and the division of some comets into two or more parts, each having coma, nucleus, and tail of its own, shows that the nucleus cannot be, in every case, what Dr. Huggins seems here to suggest. Dr. Huggins has done well in saying (though scarcely with sufficient emphasis, considering how often the mistake is repeated) that “though many telescopic comets are of extremely small mass, nucleus included—so small, indeed, that they are unable to perturb such small bodies as Jupiter’s satellites—yet we should mistake greatly if we were to suppose that all comets are ‘airy nothings.’ In some large comets the nucleus may be a few hundred miles in diameter, or even very much larger, and may consist of solid matter. It is not necessary to say that the collision of a cometary nucleus of this order with the earth would produce destruction on a wide scale.” It is even more necessary to correct the widely-spread misapprehension as to the relations between meteors and comets. We hear it stated that the nucleus of a comet is made up of meteoric stones (Professor P. G. Tait says—for unknown reasons—that they resemble “paving stones or even bricks”) as confidently as though the earth had at some time passed through the nucleus of a comet, and some of our streets were now paved with stones which had fallen to earth on such an occasion. As a matter of fact, all that has yet been proved is that meteoric bodies follow in the track (which is very different from the tail) of some known comets, and that probably all comets are followed by trains of meteors. These may have come out of the head or nucleus in some way as yet unexplained; but it is by no means certain that they have done so, and it is by many astronomers regarded as more than doubtful.