48 TIMBER AND TIMBER TREES. [CHAP. 
other woods; while, if kept wholly submerged, there is 
scarcely any limit to its endurance. 
Oak timber! has, however, one drawback. It con- 
tains a powerful pyroligneous acid, which prevents 
its general employment in immediate contact with 
iron, as the metal, whether used for fastenings or other- 
wise, is subjected to a rapid corrosive action, while 
the timber is also liable to suffer by waste an 
deterioration. ; 
British Oak timber has, for ages past, been a most 
important article in ship-building in this country, and it 
is still used for this purpose to a very great extent, not- 
withstanding the present very general use of iron asa 
substitute for it. 
It was only within the last few years, that it was 
felt the quantity of Oak produced in England would 
soon be inadequate to meet the great and increasing 
demand for it, and that it was necessary efforts should 
be made to supplement it by the introduction of 
foreign Oaks and other hard woods for ship-building 
purposes. 
To show this great necessity it will be. sufficient to 
state, approximately, the store of ship-building timber 
which it was thought necessary to maintain at Woolwich 
Dockyard in the several quinquennial periods of the 
quarter-century ending in 1865. It will, apart from the 
ordinary demands of the private trade, serve to illustrate 
in some degree how large must have been the supplies 
annually required for all the royal dockyards, taken 
collectively, in order to replace the ships that were 
worn-out or had become obsolete, and to keep the 
ships of the royal navy up to the strength called for by 
the times. 
