426 Elimination of Algce in Lochs and Ponds, [Sess. 



present in this sheet of water for at least a century, and in 

 some seasons it increased to such an extent as to render the 

 loch very unsightly, not to say offensive. The first step 

 necessary was to ascertain the amount of sulphate of copper 

 wliich would probably be required to give a solution of one 

 part in a million gallons, that being the strength recom- 

 mended by the American experts for a case of this kind. 

 The loch is a mile in circumference less 200 yards, is pear- 

 shaped, and covers nearly 23 J acres. After careful calcula- 

 tion, the amount of water contained in it was set down as 

 fully 150 million gallons. Accepting the finding arrived at 

 from the experiments in the Laboratory at Washington, 

 namely, that 50 lb. of copper sulphate to 25 million gallons 

 of water is equal to a strength of 1 in 4 millions, it was 

 estimated that half a ton, or 1120 lb., of the sulphate would 

 be a sufficient quantity. As it happened, the town of 

 Selkirk until a comparatively recent period drew most of 

 its water-supply from The Haining loch, and the old 

 public well still stands in the market-place, deriving water 

 from the same source, though the well is now only used 

 as a watering-trough. Before the application of the copper 

 sulphate the precaution was taken to cut off this supply 

 temporarily from the loch, lest by any chance harm should 

 happen to the lower animals. The 9th of August 1911 was 

 the date when the experiment was carried out. Two boats 

 were used, and to these were attached two or three wide- 

 meshed bags containing each about 14 lb. of the sulphate. 

 The boats were then rowed very slowly up and down the 

 loch, and the bags refilled until the whole 1120 lb. had been 

 dissolved. This occupied fifteen hours — from 6 A.M. till 

 9 P.M. Next morning the water had a greyish hue, from the 

 amount of dead Algse floating in it. On August 23 the 

 Professor wrote to me as follows : " You will be interested to 

 learn that, a week after the original experiment, as the greyish 

 dead matter did not settle down, I followed up a hint of the 

 American Bulletin which says that when there is much 

 organic matter in the water, lime aids precipitation of the 

 copper and the stuff it has killed. I sowed one ton of lime 

 over the surface of tlie loch (as one sows corn in handfuls), 

 and next day the ashy-grey or whitish -green colour had 



