12 HYDRQCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



pies secured were very superior in tightness to the grades now gen- 

 erally supplied in California for the fumigation trade. Although this 

 collection contained samples of the very tightest ducks and drills 

 manufactured, it was decided to accept the offer of one of the largest 

 cotton-goods concerns to carry on special experiments in weaving for 

 the benefit of this investigation. As a result of these experiments 

 samples of 6-ounce, 7-ounce, and 8-ounce drills were furnished. 

 These are easily the most tightly woven drills the writer has ever 

 seen and some local cloth* experts are of the same opinion. Each of 

 these samples was made very tight by forcing in more threads than 

 are found in the tightest drills on the market. 



Experiments with new tent material. — Tents were made of each of 

 these 7-ounce and 8-ounce special drills and tested in the field. Part 

 of an orange orchard of trees from 10 to 15 feet tall winch were 

 severely infested with the purple scale was fumigated during Sep- 

 tember, 1909. The point was to determine at what strength eradi- 

 cation would occur with these new tents. Both potassium cyanid 

 and sodium cyanid were used. On examining the results with these 

 new tents it was found that schedule No. 1 (see p. 34) with potas- 

 sium cyanid produced eradication, whereas with the ordinary fumiga- 

 tion tents a 1^ schedule was required to secure the same results. 

 With the sodium cyanid it was found that the equivalency of between 

 a three-fourths schedule and a No. 1 schedule produced eradication, 

 whereas it requires the equivalent of a 1J schedule with ordinary 

 tents to reach the same degree of efficiency. These results with both 

 potassium cyanid and sodium cyanid show that this new tenting 

 material requires at least one-fourth less of these chemicals than the 

 regular tents now largely used. This would mean a saving of fully 

 25 per cent on the amount of cyanid required in field work if the 

 tighter tents are used. 



What cloth to use. — Cyanid is the most expensive element in fumi- 

 gation work. A saving of 25 per cent on this article means a materi- 

 ally lessened cost for the process. This better and tighter special 

 tenting material may be somewhat more expensive than the present 

 inferior goods used, yet the amount of cyanid saved as well as the 

 superior results secured from its use will in the long run many times 

 offset the additional initial cost. The writer would advise either a 

 7-ounce or an 8-ounce weight of these new goods for commercial 

 fumigation as superior to any cloth lie has ever seen. There appears 

 to be little difference in tightness between the two weights. By 

 reason of its greater weight the 8-ounce drill might prove more dura- 

 ble, whereas on the other hand the 7-ounce weight is easier of manip- 

 ulation in the field: This special grade of drill advised by this inves- 

 tigation can be purchased at any of the dealers in fumigation tents, 

 in Los Angeles, Cal. Anyone making an investment of the amount 



