BY 11. I. JENSEN. 71 



2. Decomposition of the rock is faster than usual, because of 

 its rather coarse texture, the fair average rainfall (30 inches per 

 annum), and the abundance of springs in the trachyte area. 



3. Much of the soil is derived from tuffs and breccias 



, Absence of scrub on the basalts here is due to the same cause 

 as in other western localities, viz., the rainfall is too irregular to 

 sustain a scrub in the absence of springs. 



The volcanic rocks of the Fassifern Scrub are all Post-Triassic 

 and probably Post-Cretaceous There seems to have been an old 

 series of dolerites anterior to the trachytes, but I have not satisHed 

 myself on this point. The remaining links of the sequence, viz. — 

 (1) Trachyte, later (2) Andesite, and still later (3) Basalt. — I have 

 found satisfactory evidence for. 



All the volcanic rocks of the Fassifern Scrub may be looked 

 upon as belonging to the denuded remnant of one great volcano, 

 a fraction of which remains in Mt. French. The latter consists 

 of massive columnar trachyte; some of the columns reach a length 

 uninterruptedly of some 250 feet. The columns of the North 

 Peak are vertical, and this part of the mountain is probably a 

 flovv. 



To the W.S.W. of Mt. French lies Mt. Edwards, which like- 

 wise consists of columnar trachyte. South of Mt. Edwards lie 

 the peaks of Mt. Greville and Mt. Alford, both consisting of 

 trachyte and quartz-trachyte. All these are isolated peaks, the 

 plui;s of independent denuded volcanoes. On these mountains 

 and on the summit of Mt. French the vegetation is of a poor 

 forest-type as in the Glass House Mountains. The trees which 

 follow the trachytes are Ironbarks {E. c?-e6rrt and E. melanophloid) 

 and Moreton Bay Ash {E. tesselaris). On the poor, very siliceous 

 sandstones which occur west and south-west of the Fassifern 

 Scrub, the forest-trees consist of Spotted Gum {E. macidata), Blue 

 Gum (E. tereticornis), Ash (^E, tesselaris), Wattle (chiedy Acacia 

 decurrens). Box {E. hemiphloia). On the richer flats and on hills 

 which are cut by dykes, occasional Bloodwoods {E. corymbosa), 

 occasional Dogwood-trees {Jacksonia scoparia), and, near water- 

 courses. Apples [Angophora intermedia and A. subvelutina), Iron- 

 bark (E. crehra), and Callistemon or Bottle-Brush. 



