ASTRONOMY FOR 1889, 1890. 153 



UHiin spots are only seen in low latitudes, at about the time of mini- 

 nuim spots near the equator cease to appear, while a fresh series of 

 spots break out a great distance from it, and thenceforward to the 

 next minimum the mean heliographic latitude of the spots tends to 

 decline continuously, until at length spots are again seen only in the 

 vicinity of the equator. This law held good, Professor Spoerer shows, 

 for the minima of 1G19, 1755, 1775, 1784, 1833, and 1844, and to some 

 extent for that of 1G45. 



Second : Though in general a predominance of spots for a time in 

 one hemisphere is sooner or later balanced by a corresponding predom- 

 inance in the other, this is not always the case, and Professor Spoerer 

 calls attention to three periods in which the southern hemisphere was 

 decidedly the more prolific. The first was from 1621 to 1625, there be- 

 ing no northern spots in 1621 and 1622, and but few in the three fol- 

 lowing years. Another is the present period, for from 1883 to the pres- 

 ent time the southern spots have been nearly twice as numerous as the 

 northern. But the third was the most remarkable, for from 1672 to 

 1704 we have no record of any northern spots at all ; and Cassini and 

 Maraldi expressly declared, on the appearance of a northern spot in 

 1705, that they did not recollect ever to have observed a spot in that 

 hemisphere before. Northern spots continued to be infrequent until 

 1714. 



Third : For a period of about seventy years, ending in 1716, there 

 seems to have been a ver^^ remarkable interruption of the ordinary 

 course of the spot cycle. In several years no spots appear to have 

 been seen at all, and in 1705 it was recorded as a most remarkable 

 event that two spots were seen on the sun at the same time, for a sim- 

 ilar circumstance had scarcely ever been seen during the sixty years 

 previous. So far as the observations go, the " law of zones" also seems 

 to have been in abeyance, for no regular drift was apparent, the mean 

 latitude being low — about 8° or 9«^— during the entire time. 



Professor Spoerer is still continuing his researches into ancient sun- 

 spot records, and hopes to be able to examine the manuscripts of Plant- 

 ade (1705-1726) and of Flaugergues (1794-1830). (B. W. M. Monthly 

 Notices B. A. S., February, 1890). 



Attention should be directed to a paper in the Monthly Notices for 

 December, 1890, by Rev. A. L. Cortie, S. J., on the sun-spot observa- 

 tions made at Stonyhurst in the years 1882-89. 



A comparison of sun-spot statistics for 1878 with the records of 1889 

 gives a sun-spot period of exactly 11 years, and it seems probable that 

 the real minimum occurred about the end of 1889. This probability is 

 increased by the appearance on March 4, 1890, of a large spot in helio- 

 graphic latitude 4-34o, vvhich during its period of visibility in a semi- 

 rotation of the sun passed within one-sixth of the sun's diameter from 

 its northern edge. During the wliole of the year 1889 the southern 

 hemisphere of the sun manifested greater activity than the northern; 



