1872.] Further Researches among the Plants of the Coal-measures. 435 



Terrestrial Magnetism, No. XII.," by General Sir Edward Sabine, K.C.B., 

 and President of the Royal Society, the annual decrease of the westerly 

 declination, in the interval 29*5 years, over various geographical districts 

 is thus shown : — 



Shetland Islands and N.E coast of Scotland, between 60th and / 



56th parallels .. 8"24 



East coast of England, between 56th and 51st parallels .... 7*78 

 South coast of England, between 51st and 49th parallels . . 1 



Dungeness to Scilly Islands with the Channel Islands . . . . J ' 



{Greenwich Observatory 714) 



Irish Channel, between 52nd and 54th parallels 7*10 



Hebrides and west coast of Scotland, between 56th and 58th 



parallels 6 '85 



Ireland, S.W., West, and N.W. coasts, between 52nd and 55th 



parallels 6 - 26 



It is thus seen that in the area included by the shores of the United 

 Kingdom the change was greater on the eastern than on the western side; 

 as also that in the higher parallels of latitude of this area the change was 

 greater than in the lower parallels. 



By a further comparison of results as observed within the last ten to 

 twelve years, at the same stations within the same geographical districts, 

 the following approximate values of the present rate of annual change 

 (westerly declination decreasing) are obtained : — 



Shetland Islands and N.E. coast of Scotland . . 11*2 



East coast of England (Bridlington) 10'3 



South coast of England (Plymouth) 7*9 



Scotland, W. and N.W. coasts 9*5 



Ireland, S.W. coast 6*6 



These values are in satisfactory accordance with those obtained in the 

 interval (1865-71) at the following fixed magnetic observatories : — 

 i 



Greenwich. . 8 -33 mean annual decrease of westerly declination. 



Kew 8-08 „ „ „ „ 



Stonyhurst 7*85 „ „ „ „ 



VI. "Notice of further Researches among the Plants of the Coal- 

 measures. " By Prof. W. C. Williamson, F.R.S. Received 

 June 1, 1872. 



Fallowfield, May 3, 1872. 

 My dear Dn. Sharpey, — In my memoir on Calamites, published in the 

 last volume of the 'Philosophical Transactions,' I gave two figures of sections 

 of a plant (plate 25. fig. 16 and plate 28. fig. 39) supposed to be a Calamite, 

 but respecting the Calamitean nature of which I expressed my doubts in a 



