330 T'ransactions.— Geology. 
This led me to enquire if there was a law of deposit, and, in going over all 
the surveys and levels to be obtained in this Province, I found that all were 
more or less deficient in completion, excepting the very careful survey of the 
Taieri Plain by Mr. Adam Johnston. Here the information was as complete 
in every respect as could be desired, though the extent of deposits are very 
small in eomparison with those of the Canterbury rivers. However, the 
essentials were the same, viz., alluvial deposits spread out over a plain from a 
narrow gorge in mountains running parallel with the plain. Thus the deposits, 
as brought out, had free scope for extension over 180 degrees of the horizon, 
and the result is precisely that of what may be seen in the “ tailings” of many 
of our gold workings. The Taieri, bearing the débris from mountain glaciers 
originally, and now that of floods, issues on the plain at Outram Bridge, and 
meets the low-water mark of the tide at Adams’, a distance of 121 miles 
measured by the sinuosities of the channel. The difference of level between 
the river, in its ordinary state, at Adams' and Outram Bridge, is 17:57 feet ; 
and the levels of intermediate distances are given respectively, showing a curve 
of a very decided contour. The curve is neither that of the hyperbola nor 
circle. With the data given, and by the formula already used in given cases, 
it was compared by computation with the parabola, but found not to accord 
therewith. It was then tested by the properties of the ellipse, with the 
following result, so nearly approximating that it may be said to be one and 
the same :— 
Bv ELLIPSE. By Survey. DIFFERENCES. 
At Outram Bridge M we 0000 — 4. 007000 ВИ 
11:55... LOTS a 
n : : LI ... 13920 o 20 
At'intermediate points >... 1500 .. 1495... 011 
TIS na йе дор 
At Adams’ Accommodation House.. 2 '57 ӨЙ. c5 400 
Thus, in this instance (and I have no doubt the agreement will be the same 
in all similar conditions of water scooping out the gravel, clay, and mud), water 
descending to its level, through alluvial soil, digs or scores out its bed to the 
curve of the ellipse ; and thus, in a remarkable manner, imitates the semi- 
liquid glacier in its operations on the valleys of the earth. 
This, then, is the law of erosion, but not of deposit, the next subject of 
enquiry. In searching for a law of deposit we again refer to Mr. Johnston's 
survey, which gives us ample data. Taking his levels between the same points, 
we find the distance by flood-channel 59,730 feet, or about 11 miles : ; and the 
difference of level 30 feet. Levels are also given at intermediate points, 
resulting in a decided curve. In this case the summit of the alluvial banks 
are taken, the effect of many floods, and not of one in particular; as 
Mr. Johnston's map elicits the curious fact that Separate floods have very 
