374 DR. C. CHREE: ANALYSIS OF RESULTS Ki:<>M TUF. FALMOI'TI! MAHM.K) 



Falmouth since 1891. They have been under the direct supervision of Mr. KITTO, 

 the Superintendent of the Observatory, who lias acted throughout as magnetic 

 observer. The behaviour of the vertical-force magnetograph has been indifferent, and 

 the curves from it have not been measured ;* but the declination and horizontal- force 

 magnetographs have worked satisfactorily, and the data obtained from them on the 

 Astronomer Royal's quiet days have appeared in the ' Annual Reports of the Royal 

 Cornwall Polytechnic Society,' and also in the Royal Society's ' Proceedings,' or the 

 ' Reports of the National Physical Laboratory.' 



The proposed investigation met with the hearty support of Mr. WILSON Fox, 

 Honorary Secretary of the Royal Cornwall Polytechnic Society, and of Mr. KITTO, and 

 the latter kindly took a number of special curve measurements necessary for the inquiry. 



The Falmouth magnetographs, though resembling those at Kew in the size of the 

 magnets and in their general design, are by another maker, and differ in a variety, of 

 minor points. Thus the scale of the declination magnetograms is considerably less 

 open than at Kew, and the temperature coefficient of the horizontal-force magnet is 

 so small that its sign even is uncertain. Also the Falmouth magnetic chamber has a 

 considerably smaller diurnal variation of temperature than that at Kew. Again, the 

 position and climate of the two observatories are widely different. Kew is in the 

 level plain of the Thames Valley, some 60 miles from the sea, but the magnetic 

 chamber is only some 20 feet above mean sea level. Falmouth Observatory, though 

 close to the coast, is about 160 feet above sea level. Kew possesses, for England, an 

 almost continental climate, whilst Falmouth enjoys the equable temperature of the 

 Cornish coast. 



From these considerations there is strong reason to believe that any phenomenon 

 observed in the records of both observatories is not due to instrumental defects or to 

 purely local peculiarities. 



Falmouth Observatory is situated in 50 9' 0" N. latitude, 5 4' 35" W. longitude. 

 Local noon is thus 20 minutes 18 seconds after Greenwich, 19 minutes 3 seconds after 

 Kew. 



An 11-year period, 1890 to 1900, was employed in (A). For Falmouth I have 

 employed a 12-year period, 1891 to 1902. This includes all the data published when 

 the investigation commenced, and secures a sun-spot minimum period, 1899 to 1902, 

 equal in length to that of sun-spot maximum, 1892 to 1895. The mean sun-spot 

 frequency after WOLFER for the whole period and the above sub-divisions was as 

 follows : 



* [MarrJi 31, 1905. The working of the instrument was improved in 1902. The curves for 1903 and 1904 

 have !>ecn tabulated since the above was written. The results appear satisfactory and are being published.] 



