86 TIMBER AND TIMBER TREES. [cHAP. 



thoroughly, and when this ship comes under repair it will 

 be ascertained by comparison with the other side how 

 far it is useful in preventing decay. The Admiralty 

 also ordered the faying surfaces of the frame timber and 

 planking of the Tenedos and Spartan, the former build- 

 ing at Devonport, and the latter at Deptford Dockyard 

 in 1868, to be carbonised by this process, in the hope 

 that it will retard the formation of fungus on the sur- 

 faces, on which it frequently forms with rapidity ; but, 

 as neither of these ships has yet been opened for 

 repairs (1875), it is uncertain whether any good results 

 have come of the experiment. 



Experience has shown that many soluble substances 

 of a poisonous or antiseptic nature, will delay or prevent 

 the processes of rot or putrefaction to which all timber is 

 liable. Modern botanical research has proved that this 

 is owing to the fact that the poisons used kill the spores 

 and niycelia of the various parasitic and other fungi 

 which destroy the timber by (i) feeding upon the sub- 

 stances in the wood-elements, and (2) piercing the walls 

 of the latter, or even dissolving them, and so weakening 

 the structure. 



But experience has also shown that there are enor- 

 mous difficulties to be overcome before a piece of wood 

 can be interpenetrated by any solution, however dilute. 

 These difficulties never are overcome in practice, because 

 where large pieces of timber are to be operated upon it 

 is impossible either to give the time or to apply the 

 pressures necessary for forcing the solution into the 

 deeper layers of wood. 



In discussing this subject it must never be forgotten 

 that wood is not a mere porous body, like a piece of 

 brick or gypsum, but that it has a complex structure, as 

 already described in the introductory chapters. This 



