186 w. n. benson. 



Explanation of Plates. 



Plate VI, fig. 1 — Theralite from Barrington Trigonometrical 

 Station. Note the zoned augite, large 

 ilmenites, cloudy felspar and clear white 

 nepheline x 4. An enlarged drawing of 

 this white patch is shown in text fig. 3. 



,, 2 — Olivine dolerite from the above locality, with 



plagioclase, augite, olivine, and natrolite 

 x 12. 



,, 3 — Olivine dolerite from the Peel River gravels 



showing basaltic ground-mass x 11. 



„ 4 — Nepheline basanite, Square Top, Nundle, 



showing augite phenocrysts, with peri- 

 pheral zone full of inclusions, olivine, and 

 hexagonal nepheline crystals in the ground 

 mass x 18. 



Plate VII, Specimen of porphyritic olivine dolerite from the Peel 

 River gravels near Nundle, with large phenocrysts 

 of titaniferous augite. Scale one half natural size. 



Corrigendum to paper entitled "The Volcanic Rocks of Hornsby 

 and Dundas," this Journal, Vol. xliv, pp. 495 -555, 1910. The 

 analysis of the Hornsby basalt, pp. 544 - 545 was made simul- 

 taneously with analyses of several other rocks, and it has since 

 been discovered that the wrong figure for titanic oxide was entered 

 through oversight, in the Hornsby analysis. A redetermination 

 has been completed and the correction must be made as under. 



Pages 544 and 545, substitute for the figures given: — 

 A1 2 3 17-94% Ti0 2 2-64%, 

 and the following recalculated norm.: — 



Orthoclase 13*34 Magnetite 4-64 



Albite 31-44 Umenite 5-02 



Anorthite 24*74 Apatite 1-34 



Nepheline 1-14 C0 2 '71 



Diopside 9-95 Water 1-12 



Olivine 4-54 100-98 



