143 



interior such ready-made Bordeaux mixtures are to the home-made 

 freshly-mixed article. One of the best known of these mixtures 

 sold in powder form was tested in two ways. In the first experi- 

 ment the powder after, being mixed with water according to the 

 directions, was thoroughly shaken up in a glass cylinder, and then 

 allowed to stand for five minutes. It was found that the suspended 

 matter (containing all the copper) had almost completely disappeared, 

 through subsidence, from the upper half of the liquid in so short 

 a time as five minutes^ — the percentage of copper in the upper 

 half of the cylinder being only I '6. Another similar cylinder was 

 filled with home-made Bordeaux mixtuie, and exactly the same 

 treatment given to it, but here the tendency of the suspended 

 matter (/. e., all the copper) to subside was very different, — the 

 percentage of copper in the upper half of the cylinder, after five 

 minutes, being 48*4. In the second experiment, the adhesive 

 property of home-made Bordeaux mixture was compared with that 

 of the mixture made from the proprietary powder mentioned 

 above. Investigations showed that in the case of leaves sprayed 

 with home-made Bordeaux mixture, the first shower of rain removed 

 only 2*92 per cent., of the copper, and the second shown 3'65 per 

 cent, of the copper— making a total washed off of 6'57 per cent, 

 of the copper. In the case of leaves sprayed with Bordeaux mix- 

 ture made from the proprietary powder the first shower removed 

 46*60 per cent, of the copper, the second shower 5*97 per cent, of 

 the copper—making a total washed off of 52*57 per cent, of the 

 copper. 



The Irish Department of Agriculture have carried on investi- 

 gations for several years past in the spraying of potatoes with 

 Bordeaux mixture, both home-made and made from spraying 

 powders, and now strongly urge the farmer to prepare his own 

 mixture. 



It is clear that on account of the marked tendency of the 

 suspended matter to settle, and of the very low adhesive powers, 

 all Bordeaux mixtures put up in powder form should be avoided. 



Ready-prepared Bordeaux mixture in paste form stands in quite' 

 a different category to the above-mentioned Bordeaux powders. 

 Through the recent chemical discoveries of Mr. Pickering, Bordeaux 

 mixture cm novv^ be prepared by a new process and put on the 

 market as a concentrated paste. From the chemical standpoint, 

 certain advantages (which cannot be discussed here) are claimed 

 for the Bordeaux mixture made from this paste over that made 

 by mixing equal quantities of copper sulphate and lime, as 

 described above. Of what value these improvements from the 

 chemical point of view will prove in practical spraying against 

 fungus pests has yet to be ascertained, for there is probably a 

 biological side to the question of the action of fungicides. For 

 the reason given below, I consider that the practical fruit-grower 

 should continue to make his Bordeaux mixture with equal parts 



