THE Conductors of the London, Edinburgh, and Dublin Philosophical Maga- 

 zine, have to acknowledge the editorial assistance rendered them by their friend 

 Mr. EDWARD W. BRAYLEY, F.L.S., F.G.S., Assoc. Inst. C. E. ; Corresp. 

 Geol. Soc. of Cornwall, and Fhilos. Soc. of Basle ; Hon. Mem. S. Afric. 

 Inst. : Librarian to the London Institution. 



