400 



Scientific Intelligence. 



Orthoclase rocks. 



Orthoclase-plagioclase. 

 Monzonite group. 



Plagioclase rocks. 



#Si0 2 

 67-82 



Granite. 



$Si0 2 

 67-73 



Acid quartz mon- 

 zonite. 

 (adamellite) 



#Si0 2 

 66-72 



Acid quartz diorite. 

 (Tonalite.) 



63-66 



Quartz-Syenite, j 

 (Nordmarkite, ,63-66 

 etc.). 



Medium acid 



quartz monzonite. 



(Banatite.) 



63-65 



Medium acid quartz 

 diorite. 





Syenite. 



49-62 | Monzonite. 



48-62 



Diorite. 



50-62 



(Plauenite, Laur- 

 vikite, etc.). 



46-52 



Olivine- Monzonite, 

 etc. 



44-53 1 Gabbros, 



etc. 



Peripheral portions of the masses at Predazzo, composed of pyrox- 

 enites, are regarded as differentiation products in place, while 

 dikes of camptonite and complementary feldspathic rocks (lieb- 

 nerite poryhyry) are mentioned. 



The order of succession of the various magmas at Monzoni and 

 Predazzo is discussed very fully and in connection with that of the 

 rocks of South Norway. In carrying out the discussion a notable 

 contribution to the origin of granite and the mechanics, etc., of lac- 

 colith formation is added with illustrations drawn chiefly from the 

 south Norwegian localities. 



The author believes that in endeavoring to discover the law of 

 succession of eruptive magmas it is wrong to confound the abyssal 

 and effusive rocks together, since the two do not of necessity cor- 

 respond. " The order of succession, basic, less basic, acid, appears 

 in fact with abyssal rocks to occur so commonly that we must 

 regard this succession as the normal one; the sudden recurrence 

 to basic is known in many localities, but appears just as often to 

 be lacking." ' 



A very thorough digest of the literature is given and it can be 

 truly said that in the light of the new petrology the author has 

 cleared up and put in order a vast mass of confused and often con- 

 tradictory information about this well known locality in the Tyrol. 

 Field geologists as well as petrographers will find the work replete 

 with fruitful and suggestive ideas. l. v. p. 



13. Mica- Per idotites in Bengal. — In two short papers by Mr. 

 T. H. Holland (Records Geol. Surv. India, vol. xxvii, 1894, Pt. 

 4, p. 139 seq.), some interesting occurrences of mica-peridotites 

 are given ; one of them, which contains over eleven per cent of 

 apatite, appears to us of especial interest in connection with 

 Vogt's work on apatite deposits (Zeitschr. fur prakt. Geol., Nov., 

 Dec, 1895). Several varieties of these rocks are described, some 

 of which break up through coal-bearing strata. l. v. p. 



14. Zusammenstellung petrographischer Untersuchungsmethoden 

 nebst Angabe der Literatur, by E. Cohen. 3d edition, 53 pp. 

 Stuttgart, 1896. — This little pamphlet, which contains a very full 

 bibliography of the literature pertaining to the various methods 

 of petrographic investigation and discrimination of rock-iorming 

 minerals, will be found a very useful addition to the working 

 library of every mineralogist and petrographer. l. v. p. 



