Tue Conductors of the London and Edinburgh Philosophical Magazine 
and Journal of Science beg to acknowledge the editorial assistance ren- 
dered them in the publication of the present volume by their friend Mr. 
Epwarp Wim Bray ey, F.L.S., F.G.S., Librarian to the London In- 
stitution. 
June 1st, 1836. 
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