1903.] the Kew Magnetographs on Quiet Days, etc. 23 



author in connection with the observations of the " Southern Cross " 

 Antarctic Expedition show a relation to sun-spot frequency similar 

 to that observed in the ranges of the diurnal inequalities themselves. 



A comparison is made between magnetic and meteorological 

 phenomena at Kew from two groups of years, the one representing 

 large, the other small sun-spot frequency. This serves to bring out 

 the insignificance of the connection between meteorological phenomena 

 at a given station and sun-spots if any such connection exists 

 as compared to the connection between magnetic phenomena and 

 sun-spots. 



A comparison is instituted inter alia between the variation through 

 out the year in the amplitude of the Fourier coefficients in the 

 series found for diurnal inequalities of the magnetic elements and 

 atmospheric temperature, making use of temperature data discussed 

 by General Strachey. It is shown that the amplitudes of the twenty- 

 four-hour term in the Fourier series in the two cases vary in a very 

 similar fashion throughout the year, but that this is not true of the 

 twelve-hour, eight-hour, or six-hour terms. Attention is also called to 

 the fact that, in the temperature diurnal inequality, the twenty-four-hour 

 term preponderates in a way that is not found in any of the magnetic 

 elements. The bearing of this is pointed out on theories as to the 

 source of the magnetic diurnal inequality. 



Attention is also drawn to a peculiarity in the variation from 

 month to month in sun-spot frequencies, which enables a somewhat 

 searching inquiry to be made as to the simultaneity of changes in 

 sun-spot frequency and magnetic ranges. 



A final section deals with the true nature of the connection 

 between sun-spot frequency and magnetic phenomena. A comparison 

 is made between Wolfer's provisional sun-spot frequencies for all days 

 in the year and for the Astronomer Koyal's magnetically quiet days. 

 The conclusion come to is, that sun-spot frequency on any particular 

 day is no guide to the magnetically quiet or disturbed character of 

 the day, and that even mean results for a month for sun-spot frequency 

 and magnetic ranges are but slightly related. It is pointed out that 

 the phenomena observed would be consistent with the view that 

 increased sun-spot activity and increased magnetic activity on the . 

 earth are due to some common source external to the sun, whose 

 effect at the same instant varies appreciably throughout the solar 

 system. If the source lies in the sun itself, it is concluded either 

 that sun-spots afford no satisfactory quantitative measurement of it, 

 or else that the effect at the earth is influenced by what takes place 

 at the sun during a considerable time. If the source of the magnetic 

 diurnal inequality be, as has been suggested by various physicists, 

 electrical currents generated by the sun's action in the upper 

 atmosphere, the cause of the increase in the amplitude of the in- 



