Observations on Mount Mary. 159 



The western end of shows the ropy structure of strained 

 viscous lava, and at one place on the south side of the cutting a 

 pear-shaped piece may be seen. 



In the lowest visible portion the rock is a decomposing finely 

 nodular and laminated basalt — the laminations simulating current 

 bedding in their diverse dips. This, also, is perhaps due to 

 strain before solidification. 



On the northern side in this lowest portion is an included 

 block of altered mudstone or clay, about 5 feet above the road 

 level. It appears to have been torn from its original bed and 

 carried along by the lava flow, or, on the other hand it may be 

 an ejected block similar to those on Mount Mary. I think, 

 howeve'r, that the former is the more probable, as the general 

 appearance of the vicinity does not convey the impression that 

 an old crater had existed there. 



Near this included mass there is a nearly vertical thin band of 

 hard vesicular basalt, which may be a small dyke, or a harder 

 portion of the main flow, as, though there is a .sharp break in the 

 western side between it and the containing decomposing nodular 

 fcasalt, it seems to merge gradually into the decomposed rock on 

 the eastern side. 



Section on Road on Western Bank of Werribee River. 



This section runs north and south, parallel with the stream. 

 It is only about 100 feet long. The lowest portion consists of 

 nodular, decomposed, massively-jointed basalt, with patches of 

 hard, vesicular basalt at the northern end, and nodules of harder 

 basalt at the southern end. At this end it is about 28 to 30 feet 

 thick, thinning considerably towards the north. 



Immediately overlying is a bed varying from 2 feet 6 inches to 

 3 feet 6 inches of friable tuff and lapilli, having an uneven 

 appearance, as if sprinkled in a dry state over a surface showing 

 considerable inequalities, due to irregular cooling and solidifica- 

 tion of the flow. The lapilli bed contains a great quantity of 

 medium-sized grains of quartz, as if portions of a coarse, sandy, 

 or gritty bed had been torn from the walls of the crater, 

 absorbed by the volcano, and later on spread over the adjacent 

 country, mixed with fragments of scoria and volcanic mud. 



