102 PROPERTIES OF WOOD. 



to become air-dry, and during this interval there is always 

 danger of infection by fungi, which do not attack dry wood. 

 When wood has been floated or rafted, part of its soluble 

 contents, albumen, sugar, gums, etc., have been removed, but 

 it is so saturated with water that the danger of infection by 

 fungi is increased. The nature of the soil in contact with 

 which the wood is used, e.g., sand, loam, or swampy ground, 

 affects its durability. Also the locality, e.g., a shaded or 

 sunny slope, a damp valley, a cool, windswept upland. [In 

 all these cases it should be noted that in order to cause wood 

 to decay three factors are necessary, heat, water and oxygen. 

 The exclusion of one of these factors suffices to preserve 

 the wood. In very wet soil oxygen is absent and wood lasts 

 long. The wood of mummy-cases is practically imperishable 

 in Egypt, where water is the absent factor. At Silchester, 

 in Berkshire, three silver-fir casks were dug from a Roman 

 well that had been filled with earth at the time of the Saxon 

 invasion, presumably about 1,400 years ago ; this wood, 

 naturally very perishable, is still in excellent condition in the 

 Reading Museum, as the clay that filled the well had excluded 

 oxygen. Tr.] 



The question whether, in order to produce durable wood, 

 fellings should be made in winter or summer is as old as the 

 hills, and is really insoluble, as it is impossible to exclude all 

 disturbing factors and experiment with one only. In any 

 case the difference in durability of the wood cut in summer 

 or winter is confined to the sapwood. [In the Forest of Dean 

 the boles of oak-trees are stripped of bark in the spring and 

 remain with their foliage transpiring moisture, and their 

 exposed wood evaporating it all the summer and autumn ; 

 this renders the wood when felled in winter very dry, and 

 must increase its durability. Tr.] 



All articles made of wood for human use are liable to wear- 

 and-tear, especially floors and street-paving. Hardness and 

 high specific weight are the best qualities to ensure durability 

 in such cases. As atmospheric influences also tend to destroy 

 street-pavement, hard, deep-coloured heartwood of any tree 

 is the most suitable material, e.g., oak, larch, pitch-pine, etc. 

 For this reason Australian hardwoods, such as Karri (K 



