10 THE VICTOHIAN NATURALIST. 



(d.) Basaltic scoria and lapilli lying unconformably on (c). 

 These rocks are of the same character as those exposed 

 in the western face of the quarry, and will consequently 

 be embraced in their description. 



The western section along its whole length and height presents 

 but one series of rocks, which, as mentioned above, are of a 

 sin)ilar character to (d). They consist of black basaltic scoria 

 and lapilli, with scattered blocks of vesicular and solid basalt. 

 The scoria and lapilli are less vesicular than in the red beds, are 

 angular in shape, and vary in size from a pea to 3 or 4 inches, 

 the majority being about a ^^-inch. The included basalt 

 boulders are often 2 feet or more in diameter. These materials 

 are quite unconsolidated and undecomposed, and they appear to 

 have a slight dip in the same direction as those of the red beds, 

 whose dip is defined, but at a lower angle. In both the scoria 

 and basalt boulders are found somewhat globular or polygonal 

 pieces (running to 2 or 3 inches in length) of granular and 

 practically unaltered Olivine, which sometimes contain blebs of 

 Diopside in varying quantity. (See specimen i. Appendix.) 

 Neither Fayalite * nor prominent pieces of Oligoclase Andesine 

 were observed. The beds just described, together with (d), may 

 conveniently be called the " black beds." The red and the black 

 beds abut against one another at the north end of the quarry. 



The smaller quarry is on the east side of Lake Bolac road, 

 and a little south of east of the Mount. Except for the 

 occurrence of a grey, fine-grained, homogeneous tuft", and the 

 smaller size of the ejected material, the rocks exposed are 

 similar to the black beds. No red beds are observable. A 

 specimen collected here is interesting on account of the mixture 

 of black and undecomposed, with red and decomposed fragments, 

 thus supporting the conclusion stated in this paper. 



Co-iidusion. — The red beds are highly decomposed, while the 

 black beds are practically unaltered ; the included minerals are 

 either dift'erenl or occur in different ways ; and the black beds 

 rest unconformably upon the red. Decomposition must have 

 taken place in the latter prior to the ejection of the former. 

 There is also evidence of this in the specimen above referred 

 to from the smaller quarry. There have therefore been at least 

 two distinct volcanic disturbances at approximately the same 

 point, separated by a considerable interval of time. The 

 red beds were first ejected, and then denuded and decomposed 

 for some depth. Such decomposition must have occupied much 

 time. Then a second eruption took place, and the fragmentary 

 material of that eruption has been in part removed, so as to 

 expose the red beds at the surface of the ground. Possibly some 



* Specimen 3 in Appendix consihls largely of P'ayalile, less decomposed than 

 the typical more ferriferous Fayalite from the red beds. As this was not 

 obtained in dtu, it is possible, from its fresh appearance, that it came from the 

 black beds. 



