34 



HYDROCYAXIC-ACID GAS FUMIGATION IX CALIFORNIA. 



great an opportunity for leakage, or that the leakage would be approx- 

 imately four times as rapid in the smaller tent as in the larger one. 

 There can be little doubt that the leakage of gas through most of the 

 tenting materials used in this State is nearly in accordance with these 

 figures. In order to secure uniformity of results this leakage must 

 be taken into consideration and small trees must receive more cyanid 

 to 100 cubic feet than the larger trees. The correctness of the fore- 

 going statement has been repeatedly demonstrated during the work 

 in the field. Reference to the leakage of gas through tents was first 





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49 



Fig. 9. — Dosage schedule No. 1, for potassium cyanid. (Original.) 



made by Prof. Woodworth, 1 and in a recent publication Dr. A. W. 

 Morrill 2 has given it a very thorough treatment. 



DOSAGE SCHEDULE. 



After having performed a large number of experiments against the 

 purple scale, and determined the dosage required to destroy this in- 

 sect on different sized trees, the writer utilized these results in pre- 

 paring a schedule of dosage to be used in fumigation. This schedule 

 (see fig. 9) has been designated " dosage schedule Xo. 1." The 

 dosages used in this schedule are entirely original with the writer, 

 being the result of experimental work supplemented by calculations 

 •as explained in the following paragraphs. After the dosages were 



J See Bui. 152, Univ. of Cal. Agr. Exp. Sta., 1903. 2 See Bui. 76, Bur. Ent., U. S. Dept. Agr., 1908. 



