154 Proceedings of the Royal Society of Victoria. 



western termination of the base line from Werribee, upon which 

 the geodetic survey of Victoria has been founded. It lies due 

 west of Melbourne, at a distance of 24 miles in a direct line. 



The shape of the mount is not quite as shown on the Quarter- 

 sheet. Instead of the unbroken rim on the south it has a 

 distinct sloping hollow there in addition to that shown on the 

 north, indicating ruptures of the rim of the old crater through 

 which the lava flowed away in both directions when the volcano 

 was in its expiring stage. The volcanic rocks visible comprise 

 vesicular and dense basalts of light to dark bluish-grey and drab- 

 grey colours ; reddish-brown and chocolate decomposing scoriae ; 

 and yellow and gi'ey consolidated tuffs. Some of the scoriae 

 weathers into brick red soil. In parts the basalt is very tough 

 and vesicular, and contains a little hyalite ; and again it is 

 fine-grained and splinters into fragments. Some portions of 

 the scoriae are exceedingly friable, and occasional blocks show 

 embedded pieces and fragments of basalt. On the northern 

 slope great numbers of masses and blocks of vesicular basalt, 

 scoriae, and consolidated tuffs occur. Some of the latter contain 

 pieces of originally fossiliferous clays now turned into dense 

 rock like porcelain-jasper, and other pieces altered only to a 

 moderate extent. An interesting feature, shown by a few small 

 pieces found at one place, is the intimate mixture of small 

 fragments of scoriae with the altered clays showing casts of 

 fossils. Owing to the absence of any natural or artificial 

 sections here the nature of the rocks forming the mass of the 

 mount can be determined only so far as the broken blocks will 

 admit. 



The fossiliferous blocks referred to occur near the summit on 

 the north-western and western slopes of the mount. No blocks 

 wei'e noticed near the foot of the slopes, the lowest found being 

 about 175 feet below the summit on the southern side. They 

 consist of altered clays and fine sandy and gritty clays of 

 brown, red, grey, yellow, and white colours. There is an 

 entire absence of carbonate of lime from the fossiliferous pieces 

 obtained, while in one or two cases a little silica was noticed, 

 forming a coating on the casts of fossils. In the more altered 

 pieces the fossils have been completely destroyed so far as 

 determination is concerned, and consist merely of badly defined 



