166 THE POTATO. 



much as possible to the underside of the foliage, as it is 

 there where the disease will first appear. In the event of 

 rainy weather setting in soon after spraying, re-spray 

 directly it is fine again. About 120 gallons are sufficient 

 to spray a statute acre, or 194 gallons an Irish acre. 



BORDEAUX MIXTURE FOR SPRAYING. The Bordeaux mix- 

 ture should be sprayed on to the crop, not watered on, 

 taking care to dew the underside of the leaves as well as 

 the upper surface. The materials required are: Copper 

 sulphate, 81bs. ; quicklime, 41bs. ; water, 40 gallons; 

 or the quantities may be proportionately reduced or 

 increased to suit the necessities of the case. Dis- 

 solve the copper sulphate by putting it in a bag of coarse 

 cloth and hanging this in a vessel holding at least 4 

 gallons, so that it is just covered by the water. Use an 

 earthen or wooden vessel. Slake the lime in an equal 

 amount of water; then add this slowly to the copper solu- 

 tion, and enough water to make 40 gallons. The mix- 

 ture is then ready for immediate use. It should always 

 be remembered that the lime must be fresh and quick, 

 not old or air-slaked ; it should be slaked gradually so as to 

 secure a smooth paste, and then have water added to 

 make milk of lime. A good test for acidity in Bordeaux 

 mixture can be secured by means of a clean and 

 good steel knife blade ; when the mixture is ready for use 

 insert the blade of a knife, and let it remain in the mixture 

 for a minute or so; if copper is deposited on the steel, or, 

 in other words, if the steel takes on the appearance of 

 copperplate, one may conclude that the mixture is unsafe 

 and likely to affect tender foliage, and more lime is 

 required. If, however, the blade remains unaffected, 

 the mixture is safe. Another test is made by pour- 

 ing a little of the solution in an old saucer, and 

 holding it up so as to get it between the eyes and the 

 light, breathe upon it gently for about half a minute; if 

 properly made, a thin skin or pellicle will form on the 

 surface of the mixture, but if no pellicle forms it will be 

 necessary to add more milk of lime. Yet another test 



