18 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



same time leaves it more pliable than any other gas-tight treatment 



experienced. The Acting Secretary of War has described this 



method as follows : 



In order to render the cloth gas-tight a linseed-oil varnish is applied. The varnish 

 is made in proportion of 100 pounds pure linseed oil, 4 pounds litharge, and 1 pound 

 of umber. This should be heated to a temperature of 130° to 200° C. for six or seven 

 hours and constantly stirred during that time. A sponge or wad of cloth is ordinarily 

 used for applying the varnish, which should be put on in very thin coats and well 

 rubbed in by hand. The addition of one coat of this varnish about once a year will 

 be found of great value in preserving the impermeability of the material. 



One coat of this oil on each side of the tenting will prove adequate 

 with most cloths. Treated cloth should be hung up to dry for 

 about two weeks, and if not entirely tight at the end of that time a 

 second coat should be applied. The cloth should be thoroughly dry 

 before it is used. 



MILDE W-PROOFIN G . 



The treatment of tents with substances to render them proof 

 against mildew is practiced to some extent. In San Bernardino and 

 Riverside Counties probably the majority of tents are dipped in a 

 solution of tannin, while in Los Angeles and Orange Counties, which 

 are much nearer the coast and consequently have a more generally 

 moist climate, tents for the most part are used without any treatment 

 whatever. This localizing of treatment to the dryer sections demon- 

 strates that for a climate like that of southern California the mildew- 

 proofing of tents is not absolutely essential. The covers used in this 

 investigation have been in use mostly in the more moist coastal 

 region for three seasons, yet they have never been affected with 

 mildew. Neither has any mildew injury to other tents been seen or 

 heard of meanwhile. The life of untreated tents in this State appears 

 to be as long as that of those which have been mildew-proofed — at 

 least this is the case with tents that are properly cared for in the 

 field as well as in storage. 



Long-used tents are now cast aside, not because of weakness due 

 to deterioration of cloth from mildew, but largely from weakness due 

 to extensive mending of holes, resulting principally from acid burns, 

 but to some extent also from use on trees containing dead branches. 

 This necessary patching, combined with general wear, limits the life 

 of the average fumigating tent to 3 or 4 years. Judging from the 

 experience of California fumigators, as well as from that of the writer 

 himself, it appears unnecessary in California to treat tents for mildew 

 if proper precautions are taken for drying them. Wet tents should 

 be spread out during the day on the ground between the trees, so 

 that the sun may reach them as much as possible. At the end of a 

 season's work they should be thoroughly dried, rolled up, and stored 

 in a dry room. 



