At the present time there are many Astronomers who are engaged in observing the spots with care; but just as formerly there are few who possess sufficient perseverance. The photographic method is excellent, but it takes much time and is costly. Some have decried, in a very unreasonable manner, a drawing made by hand: such a drawing, of sufficient size, and executed by projection by a skilful draughtsman with a telescope driven by clockwork, may stand comparison with a photograph, and this method has a better chance of being persevered in. The Rev. F. Howlett’s name must be mentioned in this connection as a draughtsman who has accomplished much by hand drawing. Though the once famous Kew observations have been discontinued, they have been replaced by a new series at Greenwich with similar appliances; whilst Janssen at Meudon has also been carrying on for a number of years a splendid course of photographic records. Schwabe, when he had collected a considerable number of observations, recognised clear indications of periodicity. Very definite epochs of maxima and minima succeeded one another at intervals of 10 or 11 years. It is true that in following out such a study the observations are certain to be in a sense a little defective. At first it was not possible to observe the Sun every day, and the gaps which resulted from bad weather necessarily added to the number of days which had to be set down as being without spots. Moreover, every method of numbering the spots must be a little arbitrary: there are often groups which, in consequence of their sub-divisions, may be counted in different ways: but in a mass of observations so considerable as those of Schwabe’s, such uncertainties will compensate for one another and will disappear in the final result. In fact the law is so striking that it suffices to cast one’s eye over his table[2] to see that. That table is both interesting and instructive at the same time. The numbers exhibited in it speak for themselves, and it is sufficient to examine them with even a small amount of attention to realise the certainty of the conclusions which have been drawn. It is therefore now to be deemed an ascertained fact that there are periodical maxima and minima in the display of spots, and that the extent of the period is between 10 and 12 years. In order to determine this value with the utmost exactness, some astronomers have had recourse to early observations. Wolf of Zurich made this the subject of some very interesting inquiries. He was able to establish the chronology of the phases which the Sun has passed through from the time of the first discovery of the spots to the present day—more than 2½ centuries. His calculations led him to a period of 11-1/9 years. Lamont fixed upon 10.43 years, but this number does not represent the more recent observations with sufficient precision.