THE VICTORIAN NATURALIST. 



bye-laws. Near Newlands Bridge a fine section was met with, 

 snowing the basalt resting directly on the denuded, upturned 

 edges of the silurian rock, which was observed to be slightly 

 altered by the heat of the basaltic flow for a foot or 

 two below the line of contact. The dip of the beds here 

 was W. 15 . No fossils could be observed in any of the 

 stratified rocks, though diligent search was made, and we 

 had to be content with suggestive markings in the bedding 

 plains. Crossing over the market gardens cultivated by the 

 industrious Celestials, and well irrigated by the Yan Yean waters, 

 proof was seen of what this basaltic soil is capable of growing 

 under favourable conditions. Continuing our course behind 

 (east of) the Stockade, evidences of the double flow of basalt are 

 observable. One flow appears to have found its way into the 

 then existing depressions in the surface, containing in some 

 places a soft calcareous material, and in others highly ferruginous 

 sand and quartz gravel deposit. Both were seen to have been 

 forced among the flowing mass, and now appear chiefly at the 

 bottom of the lower flow, and penetrating upwards into the main 

 mass — the former as an impure limestone in veins and larger 

 masses, and the latter (seen in the bed of the creek) ferruginous 

 conglomerate, compactly cementing together other portions of 

 the lower part of the first flow. In the basalt near this zeolites 

 are in places abundant; crystals of arragonite and calcite were 

 also obtained. But by far the most interesting object of this 

 excursion was the fine section of columnar basalt (similar in 

 character to that at the Giant's Causeway, in the north of Ireland) 

 in the old prison quarry, now unused, at about midway along the 

 back (east) of the Stockade. Here, for a width of 120 feet, and 

 to a height of 20 feet near the centre, the columns have been 

 quarried, in common with the slightly laminated and nodular 

 basalt flanking and surmounting them — these monoliths having 

 been sought, on account of the superiority of the stone, for 

 important parts of the prison. But few of them have been left 

 standing their full height, nearly all of them having been 

 broken off; still a fine section was before us, appearing to 

 occupy what was a deep and long depression in the land 

 surface at the time of eruption. A striking peculiarity of 

 this section is that, though the columns, all across the central 

 main body of the mass, are vertical, yet, on either side, where the 

 height is much less, the columns incline towards the centre of the 

 mass till, on the extreme flanks, they approach the horizontal, 

 appearing something as a section of the high stacks of loose fire- 

 wood seen in some parts of the bush, where all are erected on 

 their ends ; the central logs are vertical, or nearly so, while, as 

 they recede from the centre, their tops incline towards it more 

 and more, till, if the stack is still added to, the outer logs, acting 



