THE STRUCIUEE OF TIMBER. 279 



ing the wood of that tree, and if another characteristic feature 

 is wanted, it is found in the peculiar wavy lines in which the 

 vessels of the autumn-wood are disposed. These do not run 

 radially as in the oak and Spanish chestnut, but more or less 

 peripherally, that is to say, parallel to the circumference. 



Woods whose identification frequently causes some difficulty 

 are the beech, the hornbeam, the sycamore, and the alder. In 

 all of them the vessels are very small and fairly equally distri- 

 buted throughout the ring, and none has a true duramen. In 

 the sycamore all the medullary rays are distinctly visible, and 

 of about an equal size. In the alder some of the rays are bi'oad 

 and prominent, while the finer ones can scarcely be made out. 

 Moreover, in this tree one usually meets with small brown 

 patches throughout the wood called pith-flecks, which are due 

 to the borings of a larva in the cambium. The wood of the 

 beech is usually somewhat darker in colour than that of the 

 hornbeam, and the broad medullary rays are more sharply de- 

 fined. Besides, the wood of the hornbeam may almost be said 

 to be characterized by the undulating course of the wood rings, 

 which usually dip in slightly towards the centre of the tree 

 whenever they are crossed by the broad medullary rays. 



"Without the aid of carefully prepared illustrations it would 

 scarcely be possible to direct attention to the minute points of 

 distinction that enable us to distinguish such woods as birch, 

 poplar, willow, etc. From what has been said, however, it will 

 be seen that if carefully looked for certain peculiarities will be 

 found in the structure of many timbers that are most useful in 

 assisting us to their identification. Anyone who has good eyes 

 and observes carefully will easily detect those to which I have 

 alluded, and will doubtless discover others which the scope of 

 this paper prevents my referring to. 



The lecture was copiously illustrated with lantern slides and 

 specimens. 



