RECENT ADVANCES IN SCIENCE 299 



and phonolite, form the summit of the Pic de Maros. A com- 

 parison of the chemical composition of the rocks from these 

 two districts shows that they are chemically similar. Highly 

 potassic rocks are now known to exist within a region nearly 

 a thousand miles in length, covering areas in Java, Celebes, and 

 Borneo. 



H. S. Washington has commenced a series of papers descrip- 

 tive of the igneous rocks of Sardinia (Amer. Jour. Set. 191 5 (4), 

 39, 513). The volcano of Monte Ferru is shown to consist of a 

 core of trachyte, passing locally to phonolite, and covered by 

 a thick mantle of basalt which extends far beyond the boundaries 

 of the trachyte mass. The different varieties of these rocks 

 are described and analysed with the commendable detail char- 

 acteristic of American petrography. Small flows of analcite- 

 basalt occur in this locality, but these are described more fully 

 in another publication {Jour. Geol. 1914, 22, 742). These 

 rocks were formerly described as leucite-basalt, but the presence 

 of analcite is fully demonstrated by chemical analysis. This 

 raises the question whether " leucite-basalts " described from 

 certain soda-rich petrographical provinces {e.g. Bohemia) are 

 not really analcite-basalts. 



In the same journal J. D. Mackenzie {Amer. Jour. Set. 

 191 5 (4), 39, 571), defends his interpretation of the analcite 

 occurring in certain volcanic rocks of Alberta as of primary 

 origin. It has been suggested that this analcite, which occurs 

 in lavas of trachytic type as phenocrysts ranging up to one 

 inch in diameter, is derived from leucite by the action of soda- 

 bearing solutions. This reaction, which certainly takes place 

 under laboratory conditions, involves a 10 per cent, expansion 

 of volume, of which there is no trace in the rocks in question. 



The intrusive rock of Marston Jabet, Nuneaton, is described 

 by A. Brammall {Geol. Mag. 191 5, (6), 2, 152), as a camptonite. 

 Its lamprophyric character has been recognised by several 

 authors, but the rock still awaits a complete chemical analysis 

 to make its systematic position certain. A supplement to this 

 paper (ibid. 224) describes the suspected occurrence of em- 

 bryonic chiastolite as a result of the contact-metamorphism of 

 shales by the Marston Jabet intrusion. Chiastolite is regarded 

 as a distinct mineral species, and not as a variety of andalusite. 

 This conclusion, however, is combated by R. H. Rastall (ibid. 

 336). 



