72 The N.Z. Journal of Science and Technology. [April 
In the descriptions of Groups A and B in the above table the terms 
“ requiring lime ” and “ not requiring lime ” are used in the same sense as 
they have previously been used in articles relating to the lime requirements of 
Canterbury and Southland soils (Wild, 1917, and Wild and Anderson, 1917). 
We do not at present propose to discuss the bearing of these results 
on soil fertility in the localities under consideration. We have shown that 
the maximum figure representing the percentage of carbonate of lime in 
these soils is small, especially in soils of the Canterbury Plains Soil District ; 
but we have yet to eliminate the error introduced by the decomposition of 
organic matter under the conditions of the method employed. To do this 
is the object of experiments now in progress, the results of which we hope 
to communicate later. 
List of Papers cited. 
Amos, A., 1905. The Determination of Soil Carbonates, Journ. Agric. Sci., vol. 1, p. 322. 
Hutchinson, H. B., and MacLennan, K., 1914. The Determination of Soil Carbonates, 
Journ. Agric. Sci., vol. 6, p. 323. 
Marr, F. S., 1909. Estimation of Calcium Carbonate in Soils, Journ. Agric. Sci., vol. 3, 
p. 155. 
Russell, E. J., 1917. Soil Conditions and Plant Growth, 3rd ed., p. 218 (Longmans, 
Green, and Co., London). 
Wild, L. J., 1917. Lime Requirements of New Zealand Soils, Journ. Agric. Sci., vol. 8, 
p. 154. 
Wild, L. J., and Anderson, J. G., 1917. On the Absorption of Lime by Soils, Trans. 
N.Z. Inst., vol. 49, p. 466. 
SOME NOTES ON THE ENGINEERING SURVEY OF 
THE PROPOSED ARAPUNI DAM SITE.* 
By C. B. Sealy, Arapuni. 
; “A ' 
The establishing of a hydro-electric-power station at the Arapuni Gorge, 
on the Waikato River, having been proposed, it became necessary, after 
the initial survey had resulted in the preliminary selection of a dam site 
and power-house site, to examine rigidly and systematically the founda¬ 
tions and rock strata at and in the vicinity of the proposed dam site. 
It is this engineering survey or examination that it is now proposed to 
describe ; and in order that a description of the work now in hand may be 
clearly understood it will be advisable to refer briefly to the proposed general 
scheme (see plan, fig. 1). 
The topography of the locality may be pictured as follows : On the 
western side of the river, at the foot of a hog-backed hill, there occurs 
an old river-bed of the Waikato, leaving the present gorge just above the 
proposed dam site, and running roughly parallel to, but 130 ft. above, the 
existing river-course, separated from it by a low fern-covered ridge. It is 
into this, its old bed of bygone centuries, that it is proposed once more to 
divert the river by the erection of a dam to a height about 146 ft. above 
present water-level. This old channel will need to be deepened and widened 
somewhat in places, and will then form a natural head-race, along which 
the water will be conducted, at a maximum velocity of 4 ft. per second, 
* Paper read before the Auckland Branch of the New Zealand Society of Civil 
Engineers, Hamilton, 25th October, 1919. 
