b NOTES ON THE PROPERTIES OF WOOD. 



Plate 43, figure 1, represents English oak, of the best quality. To 

 this kind of oak belongs the Quercus pedunculata, and the Quercus 

 sessiliflora. The fresh cut of such is a yellow straw colour, sometimes 

 of a rose colour. The annual rings show a fine glossy grain which allows 

 it to take a fine polish. The horny layer of three to five millimetres is 

 quite distinct from the cellular portion, and the pores are very little to 

 be seen. 



■ This kind of oak is very sensible to the influence of the atmosphere. 

 In damp weather it swells, and in dry weather it contracts considerably. 

 This makes it liable to split ; but notwithstanding this it is excellent 

 woo J, and the best suited for the ribs in a ship. The fibres hold 

 together with a great longitudinal and even transversal tenacity which 

 gives it a great resisting power. 



Plate 43, figure 3, shows the cross section of an inferior quality. It 

 is spongy ; has large pores of a pale colour, sometimes brown or reddish; 

 its deficiency has been caused by too wet a soil, by want of nourishment, 

 or of fresh air, or of some other condition requisite for its full develop- 

 ment. If such wood be ruptured it will break clean off, and a fibre may 

 be rubbed into dust between two fingers. A valuable property of this 

 kind of oak is, that it alters veiy little by the changes in the atmos- 

 phere, and it is therefore much in use for floors, furniture, and car- 

 pentry. 



Between these two qualities of oak, range a great number of others, 

 differing in their condition. 



"When trees are found to be decayed at the trunk, it must be attri- 

 b uted to an interruption of the functions of the root. It will occur that 

 one or several of the roots die, by which putrefaction is imparted to 

 the lower part of the stem, if this rot be white or black it is not very 

 dangerous ; it does not generally reach more than one foot above the 

 roots ; but when the rot is of a red colour, the wood should not be used in 

 construction or it will soon lead to decay. 



Trees arrive at an age when their wood becomes ripe, and then is the 

 proper time to fell them. This maybe seen when the top of the tree brings 

 forth no leaves in spring. Such trees are superannuated ; that is to say 

 they grow no longer ; and then they become subject to a serious evil 

 called the dial. This is explained by the following process : — We know 

 that with a vigorous tree in full growth the heart-wood contains the 

 smallest portion of water, and that its density decreases from the centre 

 towards the circumference ; when it is felled and dried, it will split from 

 the outer side towards the centre. This is not the case with a super- 

 annuated tree, in which the oldest wood begins to perish first ; and con- 

 sequently the greatest density lies between the heart-wood and the bark. 

 Now in such a tree the central wood contracts while drying, which causes 

 the splits. Sometimes splits are found in trees which bear a glossy 

 blackish aspect, and they must be distinguished from those just men- 

 tioned. Thev extend from the circumference towards the heart, and 



