8 N. J. Agricultural Experiment Stations, Bulletin 355 



low. This is in efifect what occurs in the greenhouse, as the 

 great concentration of gas in the comb can have no effect upon 

 the plants or insects upon the benches. 



Peculiar effects are sometimes noted in measuring the con- 

 centration of the gas. For instance, in many cases the concen- 

 tration of gas might be highest in the right-hand side of the 

 house, while in others the center of the house would have the 

 greatest concentration. These differences in concentration may 

 be due to air currents in the house, which carry the gas lO 

 various parts of the house, or to layers of air of different tem- 

 perature and moisture, which might retard the diffusion of the 

 gas. This fact might account for the burning of plants in one 



■4 S 



MINUTES 



6 as 



Fig. 1. Graph of Fumigation No. 1 



A, outside bench; B, middle bench; C, center bench; D, out- 

 side collecting tube; E, middle collecting tube; F, center collect- 

 ing tube; G, comb collecting tube. 



part of the house, while plants of the same kind in another part 

 were unharmed, and also account for the failure to kill the 

 insects in some part of the house. 



The distribution of the gas may be even better seen in the 

 figures showing concentrations of gas with higher charges. 

 Thus, in No. 5, 7 and 9 with a 3/4-ounce charge to 1,000 cubic 

 feet the distribution is clearer. Here the uprush of heated gas 

 causes a great massing of the material in the upper part of the 

 house, from whence as it cools it diffuses downward until the 

 concentration becomes approximately equal throughout the 

 house, and from whence it loses in density until it falls below 

 killing strength. 



Figures 10 and 11 show very strikingly the variations which 

 may take place in the distribution of gas in the greenhouse. 



