;iir:i;Fi 



(■I ■ 



454 



heport — 1884. 



Desa of the tlierraometei'S at which the best results will bo obtained. This 

 is the place to mention a very interesting and important investigati(ni, 

 lately published by Professor W. Foerstei',' the Director of tho i5i>rHn 

 Observatory. He has fonnd that the position of one of the pillars of iho 

 observatory is subject to periodical angular displacements, and that theso 

 can be represented by means of two periods, an annual one and one of 

 eleven years' duration. This latter has agreed for three sunspot periods 

 ■with the sunspot curve. Its amplitude is as much as fourteen seconds o\' 

 ai'C. Professor Foerster seems to believe that the elfect is due to an accu- 

 mulation of heat within the pillar. His explanation seems to me to bo 

 contrary to the laws of thermo-dynamics, and I think it is much nion^ 

 likely that the change in inclination is fiue to general disturbance in tlu> 

 level of the surrounding district, which itse' would bo a consequence of 

 the eleven years period of underground temperature. Comparing togi'ther 

 the effects of winter and summer with those of the sunspot period, it is 

 found that a sunspot maximum brings with it a maximum of tempernlure. 

 The phases show a retardation, as was to be expected. The contradiction 

 of two so well-ascertained effects as those of Kocppen and Foerster is 

 very curious. Its further investigation will no doubt lead to interesting 

 results. 



Professor Balfour Stewart has taken a different line from that of pre- 

 vious workers. He takes as his variable quantity, not the temperature of 

 the place, but the daily range — that is to say, the difi'erence between the 

 maximum and the minimum temperature of the day. He also confines 

 his attention to the shorter periods of sunspot and magnetic inequalities. 

 The duration of these shorter periods has been previously determined. 

 Whether these periods are real or apparent only is not matei-ial, as long 

 as we confine our attention to the same period ot time. His latest reduc- 

 tions, undertaken jointly with Mr. Lant Carpenter,- have led. him to the 

 following results : — 



1. Sunspot inequalities around 24 and '2G days, whether apparent or 

 real, seem to have periods very neai'ly the same as those of terrestrial 

 inequalities as exhibited by the daily ♦^omperature ranges at Toronto and 

 at Kew. 



2. While the sunspot and the Kew temperature r.ange inequalities 

 pi-esent evidence of a single oscillation, the corresponding Toronto tern- 

 peiature range presents evidence of a double oscillation. 



3. Setting the celestial and terrestrial members of each individual 

 inequality so as to start together from the same absolute time, it is found 

 that the solar maximirn occurs about eight or nine days after one of the 

 Toronto maxima, and the Kew temperature range maximum about seven 

 days after the same Toronto i aximum. 



Solar Radiation. 



Tho most direct method to settle the question of variability of the- 

 solar iiiHation would be to measure directly that radiation. The peculiar 

 diflBculti. 1 which have hitlierto stood in the way of iwntinuous records 

 of solar ladiation are now gradually being overcome, and we may hope 

 before long to have some decisive evidence either for or against the 

 variability. Our knowledge at present is very vague. Professors Rosfloe 



• Aat. Nach., No. 2545, p. 1. 



Proc. lioyal Soe. ' v cvii. p. 314. 



