146 THE PROCESS OF DECAY IN TIMBER. 



one of the most wonderful phenomena of Nature, and 

 furnishes us with a clue to one of the means by which 

 life in its various forms is perpetuated upon our planet. 

 Scientifically speaking this process of decay in timber 

 may be said to commence from the moment that its 

 vegetative existence comes to a close, just as it does 

 in the dead bodies of animals; and in both cases, the 

 destruction of the tissues is due to a species of slow com- 

 bustion whereby they are chemically consumed in periods 

 of time which vary in length. In the case of timber, 

 though decay may be retarded by protecting it from 

 the action of the atmosphere, and from damp, still 

 the ultimate issue, as in the case of animal remains, 

 is certain; as according to Mr. Grantham, C.E., and 

 others, the oxygen, which during vegetation is held in 

 harmless combination, begins the work of destruction 

 from the time that vegetative life ceases. Carbonic 

 acid is evolved, and as the deterioration of the woody 

 fibre proceeds, the timber loses its flexibility and 

 strength, and finally becomes carbonized. This process, 

 it has been pointed out by Mr. Kuhlman, is hastened 

 by the driving of iron nails, etc., into woodwork, which 

 act as carriers for introducing oxygen into the substance 

 of the timber. It is probably to this latter fact that 

 the rapid decay of the hulls of " composite " ships, or 

 vessels constructed partly of iron and partly of wood, 

 was frequently due. * In what is known as " dry-rot " 

 in the timbers of ships and houses, the process of slow 

 combustion, by which the wood is eventually consumed, 

 is perhaps better seen than in any other form of decay. 

 The thickness of the timber, in these cases, does not 



* See Stevens on The Stowage of Ships and their Cargoes, 4th edi- 

 tion, 1867, pp. 612 to 614. 



