DECAY OF WOODY FIBRE. 34' 



accelerated by an elevated temperature and free unrestrained 

 access of air. The decay, on the contrary, is much retarded by 

 the absence of moisture, and by the wood being surrounded with 

 an atmosphere of carbonic acid, which prevents the access of air 

 to the decaying matters. 



Sulphurous acid, and all antiseptic substances, arrest the 

 decay of woody fibre. It is well known that corrosive subli- 

 mate is employed for the purpose of protecting the timber of 

 ships from decay ; it is a substance which completely deprives 

 vegetable or animal matters, the most prone to decomposition, of 

 their property of entering into fermentation, putrefaction, or 

 decay. 



But the decay of woody fibre is very much accelerated by 

 contact with alkalies or alkaline earths ; for these enable sub- 

 stances to absorb oxygen, although they do not possess this 

 power themselves : alcohol, gallic acid, tannin, the vegetable 

 coloring matters, and several other substances, are thus affected 

 by thern. Acids produce quite an opposite effect ; they greatly 

 retard decay. 



Heavy soils, consisting of loam, retain longest the most im- 

 portant condition for the decay of the vegetable matter contained 

 in them, viz. water ; but their impermeable nature prevents 

 contact with the air. 



In moist sandy soils, particularly such as are composed of a 

 mixture of sand and carbonate of lime, decay proceeds very 

 quickly, it being aided by the presence of the slightly alkaline 

 lime. 



Now let us consider the decay of woody fibre during a very 

 long period of time, and suppose that its cause is the gradual 

 removal of the hydrogen in the form of water, and the separation 

 of its oxygen in that of carbonic acid. It is evident that if we 

 snbtract from the formula C 86 H 22 29 the 22 equivalents of 

 oxygen, with 11 equivalents of carbon, and 22 equivalents of 

 hydrogen', which are supposed to be oxidized by the oxygen of 

 the air, and separated in the form of water ; then from 1 atom of 

 oak-wood, 25 atoms of pure carbon will remain as the final pro- 

 duct of the decay. In other words, 100 parts of oak, containing 

 52-5 parts of carbon, will leave as a residue 36-5 parts of car- 



