Thus at whatever hour any minimum occurs, another occurs _six weeks and a day later_, at about the same hour.

This would be exact enough if the period of variation were _exactly_ 2d.20m.48s., but the period is nearly a minute greater, and as there are fifteen periods in six weeks and a day, it results that there is a difference of about 13m.
in the time at which the successive recurrences at nearly the same hour take place.

Hence we are able to draw up the two following Tables, which will suffice to give all the minima conveniently observable during the next two years.

Starting from a minimum at about 11h.45m.on November 20th, 1867, and noticing that the next 43-day period (with the 13m.
added) gives us an observation at midnight on January 2nd, 1868, and that successive periods would make the hour later yet, we take the minimum next after that of January 2nd, viz.

that of January 5th, 1868, 8h.48m., and taking 43-day periods (with 13m.