242 Transactions. — Chemistry. 



at the surface is found to be fairly constant, and the same 

 remark applies to the total solids. As an instance of this, 

 three samples were taken on the 2ad December, 1897, the 

 first being from about 100 yards from the edge and from 14 ft. 

 below the surface of the lake, the second being from the 

 pump-well at the pumping-station, and the third from the 

 Council Chambers at Devonport. These samples yielded 

 chlorine 2-87 gr. per gallon in each instance, while the total 

 solids at 105° C. were 8-68 gr. per gallon from the lake and 

 Devonport samples, the pump-well giving 8-96gr. per gallon. 



To obtain the water from the bottom of the lake I used the 

 apparatus advised by Presenius, the results being satisfactory. 

 The first sample was taken at 50 ft. below the surface, the 

 water being clear and without sediment. The second sample 

 was taken at a depth of 100 ft., the water being also clear and 

 free from precipitable matter. The third sample was taken 

 from the bottom of the lake, at a depth of 157 ft., the water 

 containing a small amount of sediment. These samples were 

 taken from midway between the pumping-station and the 

 wooded shore opposite, this being stated as the deepest part. 

 A fourth sample was then obtained about 100 yards nearer 

 the wooded shore, the depth being 160 ft. This sample was 

 very turbid, and contained a considerable amount of ooze from 

 the bottom, which precipitated completely after twenty-four 

 hours. A fifth cast was made at a depth of 163 ft., no water 

 being obtained on this occasion, this being made as a test of 

 the apparatus, which was found to work satisfactorily. 



The results of analysis gave chlorine 2-87 gr. per gallon, 

 equal to chloride of sodium 4-73 gr. in each sample, while the 

 total solids gave 8-68 gr. per gallon in each instance, the water 

 from the bottom of the lake being decanted from the precipi- 

 tated matter. There is therefore not the slightest difference 

 in these two factors of the water's purity at varying depths, 

 and these agree with our analyses of samples taken at various 

 periods. 



The deposit from the lake-bottom was composed chiefly of 

 vegetable debris and ferruginous clay, together with a large 

 number and variety of diatoms, some amongst them being 

 very beautiful objects. 



The fact that Lake Takapuna is a water-supply of great 

 purity, and that its present utilisation must be very largely 

 increased in the not distant future, is, I think, more than 

 sufficient apology for my bringing this subject before you. 



