1^2 



ARBORICULTURE 



Wood Preservation, 



Flv( ).\1 the earliest anticiuitx tliorc 

 have been methods of chemically 

 treating wood, cloth, and even 

 flesh, to preserve their substances from 

 decav. The l\Qvptians were better ac- 

 quainted with this subject than is the 

 world to-day. Their nnimmies of sacred 

 animals, as well as hmnan beings, are in 

 perfect preservation after three thous{\nd 

 years have passed. The cloths. Imcn 

 wrappings of the dead, and wooden cases 

 enclosing the mummies are all preserved. 



The Xatron lakes supplied the anti- 

 septic materials, asphaltum and bitumen ; 

 salt and precious spices were also used 

 for this puropse. How well they suc- 

 ceeded is seen by the objects now found 

 in every museum. 



Other nations among the ancients 

 practiced this art, and were familiar with 

 the properties of many antiseptics. 



In modern times various methods have 

 been practiced for the economical treat- 

 ment of wood, for ocean piling where 

 the teredo is destructive, and for cross- 

 ties, bridge timbers and other purposes. 



In Europe the base of these preserva- 

 tives is creosote — a product of wood dis- 

 tillation. Owing to the greater cost and 

 value of wood there than in America, this 

 expensive process is considered econom- 

 ical. 



In America cheaper materials are 

 sought for, and coal tar products take 

 the place of creosote, but are used under 

 the name of creosoting. They are not so 

 enduring as the real wood creosote, yet 

 are suited for the more expensive works 

 of bridges and piles. 



Railway ties are not as yet of such cost 

 as to justify either of the above methods, 

 and resort i;* had to the chloride of zinc 

 solution. 



The wof)d to be treated is placed in air 

 tight chambers into which live steam 

 is forced — treating and scjjarating the 

 fermenting sap from the wood. After- 

 ward a vacuum is formed and this sap 

 and moisture arc drawn out of the cells. 

 The hot solution of zinc chloride is next 

 forced into the vessel and enters the 



pores of the wood, (due and other sub- 

 stances are supposed to fix these antisep- 

 tic materials in the wood. 



SALT. 



It has not been generally considered 

 that salt is one of the best antiseptics 

 known — and when once thoroughly im- 

 ])regnated with salt, wood is almost in- 

 destructible. This condition is maintained 

 until the salt is dissolved and washed 

 out by continuous moisture. Wood 

 which is placed in Great Salt Lake 

 for a season becomes so impregnated 

 that decay cannot take place, and in 

 this dry, semi-arid region, it would 

 be many years before the salt could be 

 removed. 



All these processes add very materially 

 to the enduring character of the timber. 

 Cross-ties of beech would last but three 

 years, and may be prolonged to sixteen 

 years, the cost of treating being insig- 

 nificant as compared with the cost of re- 

 newals. 



Artificial treatment of wood, how- 

 ever, is not to be compared with natural 

 preservatives. Substances in solution 

 with water after being dried, luay again 

 be dissolved and in time lose their anti- 

 septic power, after which the wood is 

 subject to fungus attack. 



The Catalpa gathers antiseptic sub- 

 stances from every soil in which it 

 grows, builds it into the fiber of the wood 

 and these can oidy be dissolved with 

 alcohol, hence the everlasting character 

 of Catalpa wood under conditions which 

 cause other timbers to decay quickly. 



The uuration of telegraph poles may 

 be greatly extended by di])ping the lower 

 end in a hot S(jlution of asphaltum, al- 

 lowing the w^ood to absorb a considerable 

 (|uantity of the mineral. It is absolutely 

 essential that the wood be well seasoned 

 before applying the solution, otherwise 

 the fermenting sap will cause a more 

 rapid tlecay since moisture cannot es- 

 cape. The [)oles should be coated two 

 feet higher than the surface when the 

 poles are set. 



