THE recent Prime Meridian Conference at Washington has attracted attention to the methods employed at various periods, and amongst peoples in different stages of civilisation, to reckon time. Dr. Robert Schram, on October 24, read an interesting paper on this subject before the Geographical Society of Vienna, in which he dealt chiefly with the Chinese, Hindoos, and the Jews. The three units of measurement given by Nature herself are the rotation of the earth on its own axis, the revolution of the moon in its orbit, and that of the earth around the sun; these are wholly independent of each other, and neither is an aliquot part of the others. But from the earliest times efforts have been made to connect these units; there is the attempt to balance all three, which gives the luni-solar year, or those to connect the day with the course of the sun or of the moon, from which we get the solar or lunar year. In the earliest times the most complicated of these, the luni-solar year, in which it was sought to connect and equalise all three units, was the one most in use. This is comprehensible when we recollect that now we want to fix single days as far back or in the future, as we wish, and that therefore this form of year appears complicated to us; but in primitive times it was really the most simple form of all, for the sun and moon relieved man of the trouble of reckoning days, and in the months and seasons wrote large on the face of Nature herself the hours and minutes, if we regard the days as seconds. A glance at the heavens or at the surrounding vegetation must have told primitive man the most that he wanted to know of the passage of time, and have supplied the deficiencies of his calendar. How the luni-solar year came direct from Nature herself, and also how it was to be taken as an approximate method only, may be seen in the most ancient form of the Jewish year, which was so regulated that the feast of Passover should be celebrated when, during full moon the barley, which was required as an offering, was ripe, and it must be in the first month of the year, which was then Nisan. Twelve months then were counted from this; but if at the end there was no prospect that the barley would be ripe in fourteen days, a second month, Adar, was simply intercalated, and the new year began with the next new moon. But when an exact and rigid measurement of time is required, this form of year is simply perplexing. The three main types existing down to our own day of the luni-solar year are the Chinese, the Hindoo, and the Jewish years, and each of these is treated by Dr. Schram in turn.