out with precision; we know in advance which country will pass across the field of our telescope; and the period of rotation, as already mentioned, is known to the 100th of a second. It is 24 hours 37 minutes 22.58 seconds. We also know that the Martian year contains 59,355,041 seconds, i.e. 686 terrestrial days 23 hours 30 minutes 41 seconds. But since that planet turns on its axis a little more slowly than the Earth, there are only 668 Martian days in the Martian year. In fact the Martian calendar is composed of two successive years of 668 days and a leap year of 669 days. As in our case, there is no exact number of days in the Martian year. Perhaps their calendar has also been reformed several times without being made perfect. But let us hope that they are not as stupid as we, with our months of 28, 29, 30, and 31 days, and calling the ninth, tenth, eleventh, and twelfth month the seventh, eighth, ninth, and tenth respectively; with our disagreement about dates, Russia only arriving at the 1st of January when the rest of the civilised world has reached the 14th; with our three kinds of days: the civil day which commences at midnight, the astronomical day which commences the next midday, and the naval day which commences the previous midday; we who waited thousands of years before we could fix an exact hour, because we counted from conventional meridians, and the various countries could not agree upon the single meridian. Being probably more advanced than ourselves in its planetary age, Martian humanity is most likely more reasonable and is not mixed up with the littleness of frontiers, dialects, customs, national rivalries, etc. For a long time already, no doubt they form a simple unit. One may also suppose that they do not celebrate their new-year festival and its rejoicings amid the winter frosts, but in the hopeful days of the equinox. * * * * * One of the most curious observations which have been made on this neighbouring planet, or rather which have, apart from the canals, attracted the greatest attention, is that of the luminous flashes. It has been said that these flashes are all seen at the edge of the disc, or beyond it. This is not correct; they show themselves on the line which separates the hemisphere illuminated by the Sun from the dark hemisphere--the line called the “terminator.” They are only seen when the globe of Mars offers a sensible phase, and only along the line of that terminator.