254 



SCIENCE PROGRESS 



I. Biotite-granite, Pfaffenberg, Riesengebirge. W. Herz, vide L. Milch, 

 Neues Jahrb . B.B. xii. 1899, p. 162. 

 II. Adamellite (Granite of Rosenbusch), Landsberg, Vosges Mountains. Unger. 

 Quoted by Brogger, Die Triadische Eruptionsfolge bei Predazzao, he. cit. 

 p. 63. 



III. Banatite (Syenite of Bonney), Croft Hill, Charnwood Forest. E. E. Berry. 



Q.J.G.S. vol. xxxviii. 1882, p. 198. 



IV. Monzonite. Brogger's average of fourteen typical Monzonites, he. cit. 



p. 51. 



V. Kentallenite (Olivine-monzonite of Brogger), Smalingen, Fahlen, Sweden. 

 L. Schmelck, vide Brogger, he. cit. p. 46. 



c 

 o 



M O 



za 



N 



% 



MgO -185 

 CaO -181 



AlfcOj 155 



FeO -101 

 RjONajO -065 



Naj.0 -044 

 KjO -041 





9 



E-T3 



o< 



133 



084 



Fig. 3. — Diagram of the Molecular Proportions of the Monzonite Series. 



Of these five analyses, the first two have silica percentages 

 above 66, and the last a silica percentage below 52. In other 

 words, Nos. I. and II. are Acid rocks, No. V. belongs to the 

 Basic division, while Nos. III. and IV. are members of the 

 Intermediate Group. 



The Iddings diagram (fig. 3) shows that the character of the 

 Monzonite Series is not unlike that of the Calc-alkali Series, 

 the chief difference being determined by the higher proportion 

 of alkalies, due to the increase in potash, which in this series 

 nearly equals the soda. This is the result of the greater pro- 



