THE LEAD ARSENATES. 



15 



tional feature, here first met with, in the work, is the fact that the safety 

 hnes are not straight but "elbowed." It would seem from the evidence 

 available that in the case of the plum a combination of medium high T and 

 H becomes dangerous more quickly as these increase than ^^^th the cherry 

 or apple. This "elbow" is also showTi in Fig. 14 giving the safety lines 

 with the commercial paste. Here the lines run on lower T and H, and in 

 cloudy weather humidities above 80, even uith low T, are dangerous. A 

 somewhat similar result following the use of the powder is given in Fig. 15 

 in the case of cloudy weather. The clear weather results differ only 

 slightly from those with the paste. 



Humlditu, 

 70 



Fig. 17. — Plum — Safety Line for All Lead Arsenates. AB, 

 safety line for spraying with any reliable lead arsenate under all 

 weather conditions; 1, neutral lead arsenate, clear weather; 

 2, pure acid paste, clear weather; 3, same, cloudy weather; 

 4, commercial acid powder, clear weather; 5, commercial acid 

 paste, clear weather; 6, neutral lead arsenate, cloudy weather; 

 7, commercial acid paste, cloudy weather; 8, commercial acid 

 powder, cloudy weather. 



The neutral arsenate, as in the case of the other trees, is much safer than 

 the acid arsenates, though the cloudy weather line (Fig. 16) for the first 

 time drops to run about along with those of the acid pastes in clear weather. 

 No "elbow" appears for the neutral arsenate. 



In Fig. 17 the various safetj^ lines are brought together on one chart. 

 The striking point shown here is that in the high humidities of cloudy 

 weather the commercial paste and powder, closely following each other, 

 drop far below the other lines. On the whole, the line AB should mark a 

 safety line, however, at or below which spraying on the plum should be 

 safe under any combinations of T and H with anj' reliable material. 



