Pond. — 0)i Percentage of Chlorine in Lake Takapuna. 241 



summer-time, to produce a rough hay for winter feeding, 

 would add materially to the nitrogen reserve by giving avail- 

 able nitrogenous food, and thus further enriching the land 

 with this most necessary constituent. 



We have by no means exhausted the subject, for much 

 remains to be done in the chemical and meteorological portions 

 of the subject ; but we have endeavoured to show how im- 

 portant the matter is, and that, in our opinion, it is capable 

 of successful demonstration. How much further these ex- 

 periments towards the production of a grazing country could 

 extend we would hardly like to hazard a guess, but that much 

 is capable of being done we are convinced. So earnestly do 

 we feel in this matter that we are quite prepared to devote a 

 large portion of our time and energy to bring this experiment 

 to a successful issue if so desired. Money is often expended 

 by our Government on schemes of far less value than the one 

 we have in view ; in this case, however, the cost to the colony 

 would be very small, whilst the beneficial results accruing 

 may be incalculable. 



Art. XXVIII. — On the Percentage of Chlorine in Lake 



Takajmna. 



By J. A. Pond, F.C.S. 



[Read before the Auckland Institute, 25th September, 1899.] 



On account of the proximity of Lake Takapuna to the sea, 

 and its being considerably deeper thaii Eangitoto Channel, the 

 question has been raised as to whether there may not be a 

 substratum of sea-water in the lake at depths below the 

 channel in question. To decide this matter I have made tests 

 of the water taken from the lake at various depths. 



Lake Takapuna, or Pupuki, is stated by Hochstetter to be 

 a volcanic crater having a depth of 28 fathoms, or 168 ft. It 

 has a superficial area of 268 acres, and its eastern edge is not 

 more than 200 ft. from high tide in Eangitoto Channel, while 

 the tidal waters of the Waitemata Harbour in Shoal Bay ap- 

 proach within 400 yards of its western edge. 



The deepest part of Eangitoto Channel is given on the 

 charts as 8 fathoms, or 48 ft., at low water : therefore the 

 bottom of the lake is, according to Hochstetter's measure- 

 ment, 100 ft. below the deepest part of the channel, estimat- 

 ing the surface of the lake at 10 ft. above high-tide mark, and 

 the rise of tide at 10 ft. 



From analyses we have made at various times the chlorine 

 16 



