76 Intelligence and Miscellaneous Articles* 



tropical and austral islands than the coal-plants present. The facies 

 of the Devonian Flora in North America is very similar to that of the 

 same period in Europe. 



Among the Devonian plants of N.E. America, Dr. Dawson re- 

 cognizes an angiospermous dicotyledon (Syringoxylon mirabile, nov. 

 gen. et sp.), established on a fragment of fossil wood collected by 

 Prof. James Hall from a limestone of the Upper Hamilton Group, at 

 Eighteen-mile Creek on Lake Erie. 



4. " On some Upper Eocene Fossils from the Isle of Wight." 

 By Prof. Dr. F. Sandberger. In a Letter to W. J. Hamilton, Esq., 

 For. Sec.G.S. 



The result of Prof. Sandberger's examination of a collection of 

 these fossils, carefully named by Mr. F. E. Edwards and forwarded 

 by Mr. Hamilton, has been to confirm him in his opinion that the 

 upper beds at Hempstead, Isle of "Wight, are the exact equivalent 

 of the marine beds at Weinheim, Jeurres, and Bergh (" Rupelien 

 inferieur" of Dumont). The freshwater limestone of Bembridge and 

 Sconce appears to correspond to the beds at Buxweilar (Alsace) 

 and Abstadt (Baden) ; and the fossils from Headon Hill and Colwell 

 Bay probably belong to the level of Dumont's " Tongrien inferieur " 

 (Lethen and Westergeln) " et superieur (Marnes superieurs au 



gypse)" 



XII. Intelligence and Miscellaneous Articles. 



ON THE ELECTROMOTIVE FORCE OF VOLTAIC PILES., 

 BY M. MARIE DAVY. 



HOWEVER carefully units of resistance and of current are 

 defined, inasmuch as these units are arbitrarily chosen, it 

 cannot be hoped that, in estimating the electromotive force of bat- 

 teries, they will directly furnish the calorific value of the special 

 work performed by the chemical actions of these batteries. It is 

 necessary to determine the value of a constant numerical coefficient 

 which, like the units of resistance and of current, could be easily 

 obtained by each physicist. 



The most simple of all batteries is Smee's. The only chemical action 

 produced normally is, the solution of zinc in acid with disengagement 

 of hydrogen. But the quantity of heat disengaged in this action 

 has been very carefully measured by M. Favre, and fixed by him at 

 18,444 for ordinary zinc, and at 18,791 for amalgamated; hence I 

 have investigated the numerical coefficient of Smee's battery. 



In a preliminary research on this battery, comprising 1 25 deter- 

 minations of its electromotive force, I obtained results varying from 

 16,886 to 20,604. The difference is two-tenths, while my measure- 

 ments would indicate a thousandth. This research demonstrated 

 the existence of seven disturbing causes : — 



1. Influence of the air dissolved in the acidulated water. — The elec- 

 tromotive force of a Smee's battery, the acidulated water of which is 

 aerated, decreases gradually as the battery works ; it is stationary 



