At the present day the science of geology is being studied more thoroughly and by more people than ever before, its advance has never been more significant. Obviously it is of the first importance that its nomenclature and terminology - growing all the time - should be clearly understood and appreciated; yet it is just here that study and publication have not kept up with the general progress. A book of this kind is therefore needed, and the present one has claims to be a pioneer. Some fifteen hundred names and terms have been carefully selected for critical consideration, a special feature being the copious quotations and references which are scattered over the whole field of geological literature (chiefly British), ancient and modern. Many of the more significant works in the history of British geology are thus brought into prominence. The "Dictionary" is meant not so much for occasional reference or for the seeking of the meaning of every out-of-way word; its aim, rather, is to be useful companion', ever ready for consultation and for the provoking of lines of thought and investigation.