910 IOWA DEPARTMENT OF AGRICULTURE. 



unpeeled and set green. This method of preservation can be practiced 

 by any one without cost. Charring, as already mentioned, is an extremely 

 ■valuable method of preservation and can easily be done at the season 

 of the year when labor is cheap. The old methods of smoke and water 

 seasoning are good, but take more time than we have in this busy age. 

 The chief value of smoke seasoning lay in the fact that the creosote of 

 the smoke was taken up by the drying wood. Lime water also hinders 

 decay somewhat, but where exposed to the weather washes off too easily. 

 Any salt or oil to be practical as a preservative of wood must be cheap, 

 easily applied, not injurious to the fibers of the wood, and not easily 

 washed out. Numerous chemical salts are used, but the best material 

 so far found is the oil of tar. This may be gotten in several different 

 forms, such as ci'ude petroleum, which while cheap, has an extremely 

 disagreeable odor and is very inflammable. Probably creosote is the most 

 common form of this oil used in the various preserving plants of the 

 country. 



Experiments in timber treating at the Iowa state college are being car- 

 ried on in co-operation with the United States bureau of forestry. The 

 accompanying photograph shows a treating tank in operation on the 

 grounds of the state college. In the experiment carried on, posts of 

 several dilferent species are being tested, such as cottonwood, silver 

 maple, boxelder, and willow. These posts were cut and peeled in 1904 so 

 that they were thoroughly seasoned before treatment. The lower third 

 of the posts are boiled in creosote for from four to eight hours. In this 

 way it has been found that the posts take up from three to seven pounds 

 of oil in the portion treated, depending somewhat upon the species. It 

 has been proved beyond doubt that if the fiber of a piece of timbei can 

 be thoroughly impregnated with tar oil that decay can not take place. 

 The problem comes in determining a cheap and eificient method whereby 

 the oil may be gotten into the post. The experiments have not been 

 under way was sufficiently long to determine absolutely the effects of this 

 method of treatment upon the various species tested. Howe'^r, from 

 similar experiments carried on by the United States bureau of forestry 

 in co-operation with whom these are being carried on at the college, 

 there is every reason to believe that willow or other soft-wooded posts 

 which have taken up four or five pounds of oil, will be much more dur- 

 able than the best cedar and oak posts. Decay always takes place just at 

 the surface of the ground or immediately below, hence it is necessary to 

 treat only that portion of the post below and to a few inches above the 

 ground. 



As the United States bureau of forestry wishes to obtain more ac- 

 curate data in the matter of fence post treatment, it has been decided to 

 continue the plant at this college for several years. During this time 

 more valuable results can be obtained than could be gotten during one 

 series of experiments. For these first experiments several residents of 

 the state furnished posts of various species which were cut and peeled 

 according to suggestions from the experiment station. Transportation 

 was paid to and from the college and one-tenth of the posts were re- 

 tained for the purpose of giving thorough tests. The remaining ninety 



