260 
knowledge of the sun remains in its present imperfect state. 
Moreover, there is little doubt that many questions of high 
physical interest depend for their solution upon our obtaining 
a more intimate acquaintance than we yet possess with the 
operations which are going on in the great centre of our 
system. It is therefore much to be desired that some of the 
many observatories which are now established in various 
parts of the world should be specially devoted to observations 
of the sun, and solar phenomena generally ; and that the 
principal magnetical and meteorological elements should be 
observed daily, without interruption, at all the regular 
magnetical and meteorological observatories. 
It may be stated that the values of the variable tempera- 
ture period, given in this paper, were derived from observations 
made at St. Petersburg, Wardoe, Gorki, Barnaoul, Trkoutzk, 
Nertchinsk, Yakoutsk, Pekin, Madras, Novo-Petrovsk, 
Lougan, Zurich, Geneva, Milan, Brussels, Greenwich, 
Jakobshavn in Greenland, and Sitka on the north-west coast 
of North America. The comparison of the variable tempera- 
ture period with the solar spot period, extends over the 
twenty -seven years 1833-59, and therefore includes three 
maxima and three minima of solar spot frequency. 
