Thomson. — Glacial Action in Otago. 329 



so huiTietUy done, lie does not at the same time, like nature, mix his earth 

 with vegetable matter, and so replenish the plains with fertile soil capable 

 of bearing fruit for the sustenance of man, but otherwise his sluicing avocations 

 are the same in principle as glacial action. 



Now if we watch sluicing operations from the commencement to their 

 conclusion, we will see a parallel to one of the most benign provisions of nature 

 most closely carried out. Let us take a hill-side bordering on a flat, such as at 

 Gabriel Gully, or "Weatherstone's ; we will see that the shingle is dej)Osited 

 from the sluice nearest the hill ; then the gravel ; furthest off is carried the 

 mud and silt. Thus, let A be the hill that is sluiced, 

 and B the plain ; first, the tailings are carried in the 

 direction of ab, then, as the earth rises, the channel 

 gets choked, so they are carried in the direction of 

 c ; this being filled iip, then in the direction of f ; 

 then of d ; then of h ; then of e ; and so forth ; 

 spreading out the mateiial in the form of a fan, in 

 separate layers, these layers varying with the quality of the soil taken out of 

 the hill. Thus, if z were blue it would be spread in a thin laj^er over the 

 portions of the fan it was carried to ; if y were red it would be spread out at 

 other parts in the same manner ; and, if x were white it woald appear at its 

 proper time and in its proper layer, and this might be done over a thousand 

 times. 



Thus the modern gold sluicer answers the enigma that puzzles the Taieri 

 farmer, when he discovers trees so far below the present surface, by telling 

 him that these trees grew at a time when the glacial sluicing operations were 

 at z, and whose tailings were deposited far below those of x and y. 



If such be the process by which the gold miner, in his sluicing opei-ations, 

 spreads out debris, drift, alluvial sludge, or tailings, in strata all over the plain, 

 such we may anticipate is the precise process by which the same matter is 

 made to cover the plains of New Zealand, wherein terrene and mountain 

 glaciers perform the functions of the sluicer. And we have only to look to 

 the neighbouring Province of Canterbury to see the effects of the process 

 developed in its most prodigious grandeur. I allude to the fan-like deposits of 

 the Rakaia, Rangitata, and "Waimakariri, on the spacious plains of that part 

 of the Middle Island. In Otago, except on the Waitaki, probably we have no 

 such examples, though we haA^e great numbers on a minor scale, which may 

 be called lateral alluvials, brought out from the small gorges of the limestone 

 ranges at Papakaio, Waikari, Kakanui, etc. But in all cases, whether the 

 deposits have been the result of natural or artificial causes, whether great or 

 small, they all appear to conform to one principle, and to adhere to one shape, 

 vertically and horizontally. 



zl 



