RECENT ADVANCES IN SCIENCE 35 



the close association of alkalic and calcic rocks in space and 

 time. For both groups of lavas the theory of differentiation 

 by the gravitational settling of the heavier crystals, and an 

 upward movement of the lighter residual magmas, is favoured. 



Shand, S. J., The Norite of the Sierra Leone, Geol. Mag. 

 1918, 5, 21-3. 



Lacroix, A., Les ortho-amphibolites et les ortho-pyrox£nites 

 feldspathiques de Madagascar, Comptes Rendus, 191 7, 165, 

 77-83 ; La composition et les modes d'alteration des ophites 

 des Pyrenees, ibid. 293-8 ; Les peridotites des Pyrenees et 

 les autres roches intrusives non feldspathiques qui les accom- 

 pagnent, ibid. 381-7. 



Cushing, H. P., Structure of the Anorthosite Body in the 

 Adirondacks, with rejoinder by N. L. Bowen, J ourn. Geol. 191 7, 

 25, 501-14. 



A new collection of highly potassic igneous rocks from 

 Southern Celebes is described by J. P. Iddings and E. W. 

 Morley (Proc. Nat. Acad. Sci. 191 7, 3, 592-7). It includes 

 phonolites, trachytes, leucitophyres, minettes, shonkinites, 

 and a new type called batukite, which is an extremely mafic 

 leucitophyre. Leucitic rocks have now been found in scattered 

 localities throughout Celebes, and have also a wide extension 

 in other islands of the East Indies. 



Prof. R. A. Daly discusses with considerable detail the 

 definition of metamorphism, and of the various sub-processes 

 which are included under that term, and arrives at the follow- 

 ing scheme of classification (Bull. Geol. Soc. Amer. 191 7, 28, 

 375-418): 



(A) Regional Metamorphism (not caused by eruptive 



bodies) : 



(1) Static Metamorphism (orogenic movement not a 

 causal condition). 



(2) Dynamic Metamorphism (orogenic movement a 

 causal condition). 



(3) Dynamo-Static Metamorphism (load-metamorphism 

 in rocks lying beneath overthrust masses). 



(B) Local Metamorphism (caused by eruptive bodies) : 



(1) Contact Metamorphism (magmatic influences in 

 control). 



