872 GEOLO(;v of glass house :\its. and district, 



and to liave tiowed over a portion of them. A similar rock is 

 described about one mile west of Walton village, apparently 

 interbedded with the Ipswich Coal Measures. Mr. Eands is 

 uncertain whether it is intrusive (laccolitic) or interbedded. The 

 former supposition is probably correct.* 



All the Australian trachytes that have been chemicall3wnvesti- 

 gated are very rich in alkali, particularly soda. The Glass House 

 Mountains trachyte probably will not prove an exception. Some 

 specimens of Oonowrin rock consist almost entirely of sanidine, 

 but the Beerwah trachyte we find to be rich in plagioclase. The 

 Mt. Mellum trachyte, like that of One-Tree Point, Tas., which is 

 soda-bearing, contains an abundance of plagioclase and faj^alite. 



vii. Miscellaneous Notes. 



The tendency of the Glass House Mountains to lie on linear 

 fissures can be readily observed from one of the most southerly 

 or northerly members of the group, e.g.^ Kound Mountain or 

 Coochin Hill. Standing on the former height, one can get an 

 excellent idea of the shape of the area on which the Glass House 

 Mountains lie, as well as of their linear arrangement. From this 

 point, fourteen or fifteen summits can easily be made out. 



In connection with the question of cross-cracking, it is interest- 

 ing to note that Mt. Mellum, Mt. Blanc and Candle Mountain? 

 south of the Blackall Ranges, are three isolated peaks situated 

 on a straight line running east to west parallel to the fissure 

 on which Beerwah, Conowrin, and Ngun-Ngun are situated. 

 Whether Mt. Blanc and Candle Mountains are basaltic or not, I 

 liave not been able to ascertain; but I am informed that the soil in 

 the vicinity of them is very rich, hence it is safe to conclude that 

 they are basaltic like Mount Mellum. The Blackall Ranges 

 extend from Conondale east almost to the raihvav line, beino- 

 approximately parallel to the two above-mentioned east and west 

 fissures. Thence the range takes a northerly trend, becoming 

 practically a continuation of the D'Aguilar Range, and running 



* Jack & Etheridge, ojo. cit. p. 350. 



