Fossil Flora of Culm Measures of Devon, and Age of Beds. 95 



paragraph that the greater the disturbed solar polar regions, the 

 greater the difference between the magnetic frequency at the equinoxes 

 and solstices. 



Conclusions. 



The conclusions arrived at in the above paper may be briefly stated 

 as follows : 



1. The seasonal variation in the frequency of magnetic storms and 

 aurorae depends on the positions of the sun's axis in relation to the 

 earth. 



2. The epochs of the greatest inclinations of the sun's axis towards 

 or away from the earth, or in other words the greatest exposure of the 

 N. or S. solar polar regions to the earth during a year, correspond to 

 those of greatest magnetic and auroral frequency. 



3. The epochs (groups of years), when the solar polar regions are 

 most disturbed, synchronise with those when the excess of the 

 equinoctial over the solstitial frequency of magnetic storms is greatest. 



" The Fossil Flora of the Culm Measures of North-west Devon, 

 and the Palseobotanical Evidence with regard to the Age of 

 the Beds." By E. A. NEWELL ARBER, M.A., F.L.S., F.G.S., 

 Trinity College, Cambridge, University Demonstrator in 

 Palseobotany. Communicated by Professor McKENNY HUGHES, 

 F.RS. Eeceived May 30, Eead June 9, 1904. 



(Abstract.) 



The carboniferous rocks which occupy an area of 1200 square 

 miles in Devon, Somerset, and Cornwall, are generally known as 

 the Culm Measures, a name first applied to them l?y Sedgwick and 

 Murchison in 1838 ; the word " culm " being an ancient Devonshire 

 term for the impure coal, which is confined to one horizon in these 

 beds in the neighbourhood of Bideford. 



Sedgwick and Murchison, in their classic memoir on the physical 

 structure of Devonshire (1840), instituted a twofold division of these 

 rocks, the Upper and the Lower Culm Measures, and this classification 

 is maintained here. At the present time, our knowledge of the Lower 

 Culm Measures is on an altogether different footing to any which we 

 possess of the Upper division. This is largely due to the work of 

 Messrs. Hinde and Fox (1895), who showed that this division is of 

 Lower Carboniferous age. The Upper Culm Measures, which form by 

 far the greater thickness of the Devonshire carboniferous rocks, are, 

 however, of Upper Carboniferous age. This was first proved by 

 De la Beche (1838), on the evidence of the plant remains of the beds 



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