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HENRY S. WASHINGTON 



however, all completely, or almost completely, altered, the prod- 

 uct being rather coarsely granular. The grains are very slightly 

 coherent with one another, and show in a very striking way the 

 distribution of such augite and magnetite grains through the 

 groundmass of certain rocks, as has been already pointed out.^ 

 The groundmass is holocrystalline, and composed largely of 

 flakes of alkali feldspar, with few laths. The augite and mag- 

 netite grains resulting from the disintegration of the biotite are 

 very abundant. Bucca refers this Mte. Lattani rock to the 

 trachytes, though, as will presently be seen, he is struck by 

 their andeistic character. 



An analysis of the rock of Mte. Santa Croce (I) made by 

 myself is given below, II being an analysis of the same occur- 

 rence by vom Rath, ^ and III being an analysis of the ciminite of 

 Fontenu Fiesole, near Viterbo,^ inserted for convenient com- 

 parison. 



Abich (p. 114) gives the silica percentage as 57.41 and the 

 specific gravity as 2.79. 



Belonging to the same group is a specimen from a flow met 

 with in the valley east of Casi, to the west of Teano. This is a 



' Cf. Jour, of Geol., IV, 270, 1896. 



= Vom Rath, Zeit. d. d. geol. Ges., XXV, 245, 1873. 



^Yi. S. V^ASHINGTON, JOUR. OF GEOL., IV, , 1896. 



