PROCEEDINGS FOR ISIKI LXXIX 



ulmost as often entirel}' difterent. It is, therefore, essential that the 

 writer or observer should in all cases state clearl}' his view of the nature 

 ■of the process by which the result has been attained. 



The terms deposited, erupted, irrupted, formed, igneous, stratitied, 

 stratiform, crystalline, metamorphic, trap, grauwacke, slate, shale, are 

 all terms of the class referred to ; and when used without discrimination 

 and explanation, as they often are, scarcely tend to enlighten the geolo- 

 gist, much less the ordinary reader. 



As regards the terms metamorphic, pseudomorphic. endomorphic, 

 etc., there have been many learned discussions, and a variety of opinions 

 have been expressed by such eminent authorities as î^aumann, Sheerer, De 

 la Eèche, Dana, Lyell, Hunt, and a host of other writers. Less learned 

 persons may, however, I thinlv, be content to accept the Anglo-Saxon 

 term altered or changed as expressing the truth ; and it may. 1 hold, be 

 believed as a further truth, that there are no rocks at the present day, 

 except perhaps some of the very youngest, to which the term, in its 

 simple and original meaning, is not more or less applicable, especially in 

 all regions of intense dynamic action. Whether the change is one of 

 form, of composition, or of texture, or of all three, is a matter of detail 

 rather of local than of geognostical import. The manner in which the 

 change has been brought about is certainly intei'esting. but is also a mat- 

 ter of detail that may well be left to the chemist and the microscopist to 

 determine and to theorize upon. But there is, I think, as much truth as 

 poetry in the statement, not generally believed, that "stones grow." 

 That, like plants and animals, they do so. however, is certain. It is 

 plainly illustrated in concretions, in crystals, an<l in crystallizations. 

 None more beautiful or more easily observed than those of water on a 

 window pane ; or in what maj" be called the sporadic manner, in which a 

 surface of water becomes ice, and which, 1 believe, is closely analogous to 

 the metamorphic action which results in the formation of granite i?i situ 

 from pre-existing either stratitied or massive rocks. 



The inquirer on these matters, however, cannot do better than make 

 use, as I have myself, with immense advantage, of the wonderful store of 

 research and personal knowledge of geogony. in all its branches, recently 

 (1895) made available by Sir Archibald Geike, the present director- 

 general of the British Geological Survey, in the second edition of his 

 '^ Text-book of Geology." This work is a truly imperial dictionary of 

 geolog}^ It is a concise history and review of geological work and 

 literature, in both of which its author has taken so large and so important 

 a share. It stands, and will stand, unrivalled. N'o working geologist or 

 student should be without it. 



Arch/ean Rocks. 



In considering this subject, it will be well first to define precisely the 

 meaning of the term and its restriction, so far as my remarks on it are 



