The vital importance of diffusing some knowledge of the leading principles of Science among all classes of society, is becoming daily more widely and deeply felt; and to meet and promote this important movement, W. & R. Chambers have resolved on issuing the present Series of Elementary Science Manuals. The Editors believe that they enjoy special facilities for the successful execution of such an undertaking, owing to their long experience—now extending over a period of forty years—in the work of popular education, as well as to their having the co-operation of writers specially qualified to treat the several subjects. In particular, they are happy in having the editorial assistance of Andrew Findlater, LL. D. , to whose labours they were so much indebted in the work of editing and preparingChamber's Encyclopædia.