72 G. W. Tijrrell — Alkaline Igneous Rocks, West Scotland. 



The mineral compositioa of the two principal varieties, estimated 

 by the Rosiwal method, is given in Table I. 



Table I. 



I. Main mass of intrusion. 

 II. Acid bands and veins. 



Chemical composition. The normal analcite-syenite of Howford 

 Bridge has been analysed by Dr. Dittrich of Heidelberg with the 

 result set forth in coluiim I of the Table below. With it are tabulated 

 for comparison the analyses of three other rocks. 



Table II. 



III. 



IV. 



Analcite-syenite, Howford Bridge, Mauchline, Ayrshire. 



Ditroite, Ampangarinana, Madagascar : Lacroix, Nouv. Arch, du Mas. 



(iv), vol. iv, p. 19, 1902. 

 Pulaskite, Cabo Frio, Eio de Janeiro. Quoted in Eosenbusch, Ele^ti. der 



Gest., 3rd ed., 1910, p. 128. 

 Phonolitic trachyte. North Berwick Law, East Lothian. Quoted in 



Geology of East Lothian, Mem. Geol. Surv., 1910, p. 130. 



