Deposition of Bedded Taffs. 25 



south, forming a blanket-like covering of even thickness, which 

 is quite unbroken. 



This feature is dia<n';iiuniatically shown on the two roads men- 

 tioned, and, after noting them from the coach, I walked out to 

 the " Corkscrew," as the winding road over the ridge on the 

 Port road is called, and examined the section with care. 



The same featm'e is shown in the town itself. Gray-street, 

 at about a hundred yards north of Commercial-road, crosses a 

 dune ridge about thirty or forty feet high. A thin tuff-sheet 

 follows the contour exactly as in the cases just mentioned. West 

 of this point, about a quarter of a mile, in a street running 

 north from the State school, well-bedded tuft's dip east off an 

 eastward facing slope of dune rock, their dip agreeing with the 

 slope. In this case 1 did not attempt to trace them over the 

 hill and down the counter sloj^e to the west. In Gray-street, a 

 thin layer of old soil intervenes between tlie dune-rock and the 

 tuff. Three of these sections are, I think, crucial, and the fourth 

 appears similar to them. It is surely impossible for material 

 to have been deposited from water in this way. At the '" Cork- 

 screw," the stratification lines can be traced for a hundred yards, 

 the beds are but the fraction of an inch thick, and there is no 

 thickening of the deposit on the flanks. The whole is perfectly 

 regular. Had the Gray-street hill been under water, the old 

 soil, at any rate, must have been swept away. 



Hitherto no reference has been made to the tuffs of other 

 countries. My aim has been to show that the tuffs of south- 

 western Victoria exhibit no characters inconsistent ^vith aerial 

 deposition, and by this, I do not mean that a strong wind-drift 

 took place, for this would produce cross-bedding, a thing I 

 have not seen, but merely a sorting of material raised into the 

 atmosphere, not by wind, but by volcanic explosion. 



Professor Judd says^ : — "Thus the tuft's covering the city of 

 Pompeii are found to consist of numerous thin layers of lapilli 

 and volcanic dust, prefectly distinct from one another, and as- 

 suming even the arrangonent which we usually regard as 

 characteristic of materials that have been deposited from sus- 

 pension in water. The fragmentary materials in falling through 

 the air are sorted " 



1 " Vok'anoes," p. 117. 



