1902.] 



Sun-spots and Terrestrial Magnetism. 



221 



Range of temperature. 



NiS. 



Ag 2 S. 

 0-0568 

 0-0737 

 0-0903 



- 182° to +15° 

 15° „ 100° 

 15° „ 324° 



0-0972 

 0-1248 

 0-1333 



The mean value for the specific heat of silver sulphide is less than 

 that for nickel sulphide throughout, but little can be deduced from 

 the results till the influence of temperature on the specific heat of 

 sulphur is known. 



" Preliminary Note on the Eelationships between Sun-spots and 



Terrestrial Magnetism." By C. Cheee, Sc.D., LL.D., F.K.S. 

 Eeceived December 18, 1902 —Bead January 22, 1903. 



I have been engaged during the last two years on an analysis of the 

 magnetic results obtained at Kew Observatory (now the National 

 Physical Laboratory), during an 11-year period, 1890 to 1900. The 

 work has been much interrupted, and is still incomplete. Amongst 

 the points dealt with is the inter-relationship between sun-spot 

 frequency and magnetic phenomena, and, as this has recently been 

 engaging attention elsewhere, I have decided to put certain of my 

 results on record at once. It has long been known from the researches 

 of Balfour Stewart, Ellis, and others, that there is a close connection 

 between the times of occurrence of greatest sun-spot frequency and 

 largest amplitude of the diurnal inequality of magnetic declination 

 and horizontal force. I have investigated whether the numerical 

 relationship between the phenomena can be adequately represented 

 mathematically in a simple way. 



A convenient basis for the investigation was presented by the publi- 

 cation by Professor Cleveland Abbe in the ' U.S. Monthly Weather 

 Eeview,' for November, 1901, of a table of sun-spot frequencies as 

 calculated by Wolf and Wolfer for a very long series of years. After 

 I had carried out all the calculations, Wolfer himself published a 

 similar table* embodying his latest corrections. The differences from 

 Abbe's table are trifling, and mainly confined to two years (1891 and 

 1892). I judged it best, however, to revise the whole of my arithmetic, 

 so as to employ Wolfer's own most approved figures. In the following 

 remarks S represents Wolfer's value for the sun-spot frequency. The 

 above-mentioned table gives the mean S for each month and for each 

 year. 



The magnetic quantity selected for comparison is the mean monthly 

 " range," meaning thereby the difference between the greatest and 



(From the National Physical Laboratory.) 



* ' Met. Zeitschrift,' May, 1902 p. 195. 



