142 THE OAK 
transverse to the fibres, 1, then that of freshly-felled 
oak = 1-09: 
(9) Durability. A mild climate and open situation 
produces the most durable oak, and it is extraordinarily 
durable under water, in the earth, or exposed to wind 
and weather, or under shelter; in the latter case it 
becomes more and more brittle as years roll by. 
The alburnum becomes rotten usually in a few years 
if exposed, and is the prey of insects if under cover. 
The heart, if sound, may last for centuries under cover 
and well ventilated, and even in earth or water will 
endure for several generations. ‘There are, for instance, 
in the museum at Kew, a portion of a pile from old 
London Bridge which was taken up in 1827 after hav- 
ing been in use for about 650 years, and a piece of a 
beam from the Tower of London of which it is stated 
that it was ‘probably coeval with the building of the 
Tower by William Rufus;’ and many other specimens 
of very old oak are known. 
(10) Burning Properties—The calorific power of 
oak wood is high, in accordance with its density, but it 
splutters and crackles and blackens too much. Never- 
theless, it produces a valuable charcoal. Hartig says 
that if we call the cooking-power of a given volume of 
beech 1, that of an equal volume of oak =0-92 to 0:96. 
(11) Peculiarities—Oak timber is apt to suffer from 
various diseases, and from frost-cracks and star-shakes, 
cup-shakes, &c., as we shall see in the next chapter. It 
often presents brittle wood, red-rot (foxiness), white-rot, 
