166 



all constituents distilling below 235° C. should be as small as the requirements for 

 satisfactory penetration will allow. 



The loss of low boiling fractions, as shown in table 16, is, of course, accompanied 

 by a corresponding percentage of increase in the higher boiling fractions remaining. 

 Furthermore, calculation of the amount of oil originally and finally in the test pieces 

 indicates that the loss falls almost entirely on these low fractions — that is, that there 

 is no washing-out effect on the whole oil. 



Inspections on these pieces continued to the following dates at the respective 

 stations: Mare Island, January, 1924; Pier 7, San Francisco, July, 1924; Oakland 

 Mole, October, 1924; Crockett, No\ember, 1925. No attack was noted on any of 

 the pieces, except those treated with fractions B, C and D at Oakland Mole. These 

 had been slightly eroded by Linuioria. 



It is interesting to note that no specimen treated in our work with whole creosote 

 was directly attacked, i. e., without having in physical contact untreated wood upon 

 which attack first started and through which it proceeded to the treated wood. Further- 

 more, two of the oils which stood up contained no low boiling tar acids. These are the 

 whole creosote minus tar acids, and a sample of oil tar distillate. There are undoubtedly 

 some tar bases, sulphur compounds, and other possibly toxic constituents in these 

 oils; but since by far the larger proportion of coal tar creosote consists of aromatic 

 hydrocarbons, it seems probable that these bodies must, themselves, be responsible 

 for a large part of the preservative value of the oils. 



The oil tar distillate apparently has a somewhat greater protective value than 

 that with which it has ordinarily been credited. With sufficiently rigid specifications, 

 it might apparently be used to some extent as a substitute for coal tar creosote, as 

 in localities where conditions are not particularly favorable to the borers, or in mixture 

 with it for greater safety. This result, however, is not conclusive without some further 

 study. 



Although no direct attack of any consequence was found on the creosoted pieces, 

 attack was perceptibly heavier where the borers went from the bait pieces into the 

 treated pieces. An inspection of the creosoted gates a:t Pier 7, San Francisco, made 

 on April 12, 1923, disclosed no evidence of direct attack on any of the treated pieces, 

 even though the bait pieces attached to them had been heavily attacked by Bankia 

 and, in all but one case, almost eaten away by Limnoria. However, in every piece 

 but one, the Bankia had gone through from the untreated bait pieces into the treated 

 pieces. In some cases, the penetration of the borers into the treated pieces was slight, 

 but in other cases they had penetrated several inches. In several pieces where a large 

 number of borers had nicked the treated wood, none had gone in far. That the borers 

 showed some reluctance to entering the creosote is shown by the deflection of the 

 burrows in the bait pieces as they approached the treated wood (fig. 22). In some 

 cases, they ceased boring and sealed off their burrows rather than enter the creosoted 

 wood. The amount of crowding existing in the bait pieces apparently has a consider- 

 able effect on the number of borers trying to enter adjacent treated wood, since the 

 only treated piece which showed no attack was the one with the least crowded bait 

 piece. Table 17 gives the complete description of these pieces at the time of inspection. 

 There was no Limnoria attack on any of the treated pieces. The data are not extensive 

 enough to warrant any final conclusion, but it seems reasonable to attribute a high 

 protective power to a treatment into which a large number of borers have started to 

 penetrate from the bait piece, if none of these borers penetrate to any depth. On this 

 basis, every fraction of the creosote shows a considerable protective value. 



The foregoing emphasizes the importance of avoiding untreated braces or other 



