70 



THE DESTRUCTIVE AGENTS OF FORESTS. 



Conditions That Discourage Decay. 



Sound wood, if properly treated or placed out of reach of 

 the elements of decay, may be preserved almost indefinitely. 

 The decay of wood is not the result of mere exposure to air as 

 is the rusting of iron but is brought about by living organisms, 

 such as insects, bacteria and fungi. Fungi and many bacteria 

 in order to live must have not only food but also a proper 

 amount of heat, moisture, light and air. Therefore, if all of 

 these requirements, or any one of them is lacking, decay from 

 these causes will be greatly lessened or made impossible. Thor- 

 oughly seasoned heartwood may have the food, the light, the air, 

 and the heat, but as long as it lacks the required moisture it will 

 not decay. Examples are numerous which illustrate the lasting 

 properties of well-seasoned wood. The interior finish of build- 

 ings erected hundreds of years often remains in a perfect state 

 of preservation. That which is exposed to the weather, as yel- 

 low poplar siding used on most of the frame houses in West 

 Virginia, is frequently found to be worn thin by long expos- 

 ure to winds and rain but yet with no sign of decay. Wood 

 kept under the water or buried deep in the ground is preserved 

 even more perfectly than that which is seasoned. In these 

 cases the supply of air, or light, or heat, or of all of them, is not 

 sufficient for the existence of organisms of decay. Further- 

 more, bacteria and the spores of fungi — ^many of which float 

 for long distances through the air — are effectually prevented 

 from coming in contact with the wood. Archaeologists have 

 frequently uncovered wooden buildings, with wooden furniture 

 and numerous smaller articles, that were used by the early 

 European races. Many of these have been buried for thous- 

 ands of years. A wooden boat, recently taken from a deep ex- 

 cavation in London, is said to have been left on the sandy shore 

 of the Thames river before the invasion of England by the 

 Romans in the year 43 A. D. A pleasure ship which was inden- 

 tified as belonging to the Roman Emperor, Tiberius, whose 

 reign ended in 37 A. D., was unearthed not long ago in a well- 

 preserved condition. Excavations in Greece, Italy, Switzerland, 

 and in other countries have brought to light old buildings the 



