ACCIDENTS, DISEASES, PARASITES. 179 



action of copper salts on common metals. It should be well 

 stirred before use. The quantities necessary in the South of 

 France are 18 gallons per acre for the first treatment, 27 for 

 the second, and 36 for the third, which are applied when the 

 leaves are fully developed. 



Bordeaux mixture is the remedy most generally used 

 against mildew, black-rot and Coniothyrium. Its general 

 use is due to its effectiveness and fairly good adherence to 

 the leaves, its small cost, and facility of preparation. We 

 will later on study the methods used for applying this and 

 other liquid mixtures. 



2nd. Blue water. Audoynaud, formerly Professor of 

 Chemistry at the School of Agriculture, Montpellier, recom- 

 mended some years ago the replacing of the Bordeaux mixture 

 (the adherence of which he considered was not sufficient, be- 

 cause the proportion of lime was too great) by blue water. 

 This compound is prepared in the following manner: lib. of 

 sulphate of copper is dissolved in 2^ pints of warm water 

 contained in a wooden vessel ; when the dissolution is com- 

 plete and the liquid quite cool, 1 pints of ammonia, of 22 

 Baum6 density, is poured into it. The liquid becomes of a 

 bright blue colour; it is diluted in 10 or 20 gallons of water 

 according to whether we require a solution at J or 1 per cent. 

 This liquid contains sulphate of ammonia, which is useless, 

 and hydrated oxide of copper, which is of a colloid nature, and 

 adheres strongly to the leaves when dry. It forms a cupric 

 deposit on the leaves which furnishes the drops of rain, or 

 dew, with the quantity of copper necessary to kill the 

 spores, and it resists the dissolving actiou of rain for a long 

 time. 



Blue water has effectively protected vines treated with it, 

 and has the advantage over the Bordeaux mixture in being 

 more lasting; it may be used without previously stirring, and 

 without risk of choking the spray pumps, as the solid matters 

 it contains are dissolved, and not in suspension. The only 

 disadvantage is that if it contains ammonia in excess it is 

 liable to burn the leaves, but it is easy to remedy this by 

 preparing the mixture some time in advance and leaving it 

 exposed to the air, when the free ammonia will evaporate. 

 However, the accidents resulting from its use induced vine- 

 growers to discard it. 



3rd. Ammonical solution of copper. This liquid was first 

 recommended to vine-growers by Bellot des Minieres, who 



M 2 



