38 SCIENCE PROGRESS 



an interesting comparison between the pockets of glaciated 

 stones found in and on the glacial lake clays of Cayuga Lake 

 Valley (New York), and identical deposits found on the tidal 

 flat adjacent to the end of the Columbia Glacier, Alaska, which 

 were dropped by small icebergs. 



Major R. A. Marriott adheres to an early explanation of 

 glaciation as due to an increase in the obliquity of the ecliptic 

 (Journ. Torquay Nat. Hist. Soc. 191 7, 1-14 (reprint)). He 

 accepts General Drayson's astronomical views, whereby a 

 glacial period culminated about 13,000 B.C. and ended 5,000 

 b.c. Submerged forests are adduced as evidence of the recency 

 of the glacial period ; but it is permissible to inquire whether 

 the evidence of raised beaches is not rather in opposition to the 

 thesis of this paper. 



Jehu, T. J., Rock-boring Organisms as Agents of Coast 

 Erosion, Scottish Geogr. Mag. 191 8, 34, I— it. 



Deeley, R. M., Mountain Building, Geol. Mag. 191 8, 5, 

 11 1-20. 



Powers, S., Tectonic Lines in the Hawaiian Islands, Bull. 

 Geol. Soc. Atner. 191 7, 28, 501-14. 



MINERALOGY AND CRYSTALLOGRAPHY. By Alexander 

 Scott, M.A., D.Sc, University, Glasgow. 



Mineralogy. — A. F. Rogers (Journ. Geol. 25, pp. 515-40, 191 7) 

 discusses the various naturally occurring amorphous substances. 

 He advocates the recognition of amorphous substances as 

 definite mineral species even where a crystalline mineral of 

 the same chemical composition is already known. Different 

 names should be used in the latter case, as, for example, tenorite 

 and melaconite for the crystalline and amorphous hydrated 

 copper oxides respectively. A short account of the more 

 important amorphous minerals is given. Naturally occurring 

 hydrocarbons and glasses are grouped together as " mineral- 

 oids," this term being used, therefore, in a more restricted 

 sense than originally proposed by Niedzwiedzki (Cent. Min. 

 1909, pp. 661-3). Many mineralogists will probably disagree 

 with the classification of pitchstone, obsidian, and so forth as 

 " mineraloids " instead of " rocks." 



H. Le Chatelier (Bull. Soc. franc. Min. 40, pp. 44-57, 191 7) 

 gives a further statement of his views concerning the con- 

 ditions of formation of tridymite and cristobalite, and some- 



