THE MONTHLY BULLETIN. 75 



use of the machine. I have talked with a number of men about 

 the machine, and have found only one who disliked it, and he dis- 

 liked it before usino; one. The only objections I have to the 

 machines are that, with ours, it has been leaking in several places 

 and keeps us on the repair most of the time. I think that the 

 graduates are a little low, as a man has to stoop to see what he is 

 doing. I believe the residue bowl is too low down, as you can 

 not pass over a very large stone without striking it, and as the 

 bowl is lead, it will be bent up in this way. I also think that the 

 generator should be made of something other than lead, as it is 

 eaten out so quickly." 



Limoneira Company. Santa Paula (three machines) : 



"After using three Owl fumigating machines for a period of 

 two months, during which time we have fumigated approximately 

 40,000 lemon trees, we feel well satisfied wuth the results obtained. 

 The killing of the scale has been very effective with a dosage rang- 

 ing from sixty to eighty per cent of schedule No. 1. Of course, we 

 had some difficulty with gas leakage from the machine early in the 

 season, but this was later overcome by proper packing and adjust- 

 ment, so that we consider them quite satisfactory from that stand- 

 point. There has been considerable deterioration in the machines, 

 including repairs, which may run up possibly to twenty-five per 

 cent of the first cost. The saving on tents by the elimination of 

 ordinary tent burning due to acid spots is one of the strong points 

 in favor of the machine. Sixty new tents which were used for at 

 least forty consecutive nights, when inspected later, revealed less 

 than a half dozen burns altogether, and these were attributed to 

 the handling of the solution at the ends of the rows rather than to 

 any fault of the machine. We believe there are several points 

 about the machine which can be improved, particularly the gen- 

 erating bowl inside the main drum or gas chamber. This is being 

 manufactured of lead, but we understand the makers contemplate 

 trying out cast iron, which we believe will be much superior." 



UNIFORMITY OF GENERATION. 



It has been thought by some that the generation of the gas might not 

 be entirely uniform for all dosages applied or perhaps the gas might be 

 decomposed on account of the heat produced in the machines. This 

 important point was not investigated by the Insecticide Laboratory and 

 is suggested for future study. The uniform and satisfactory results 

 observed and reported by the users of the machines seem to indicate 

 uniformity rather than otherwise. 



Laboratory experiments by the United States Department of Agri- 

 culture and also by the Insecticide Laboratory^ also show uniformity 

 of generation w^hen solutions of jjiire cyanide were run into diluted 

 sulfuric acid, an average of 95% of the theoretical yield being obtained. 

 The conditions were in many respects similar to those maintained in 

 the operation of the machines; that is, the cyanide was dissolved in 

 water previous to mixing with acid, and the residue was heated to a 

 temperature of 110° C. and under those conditions and as more fully 

 described in the publications cited, the results of generation were 



»U. S. D. A. Bur. Ent. Bui. 90, Part III. Cal. Agr. Exp. Sta. Cir. 72. 

 3—15527 



