272 TIMBER AND TIMBER TREES. [chap.. 



sionally seen, but can seldom be detected before, the log- 

 is under conversion. 



The alburnum, or sap of this wood, is of a dark 

 greenish colour, and differs so little in appearance from, 

 the heart-wood, that it is often difficult to distinguish the 

 one from the other. In quantity it is usually excessive, 

 frequently amounting to a fifth, and sometimes even to a 

 third, of the diameter of the tree. Few people, however, 

 regard it when appropriating this timber to works of 

 construction. 



Owing to the difficulty of distinguishing the sap, 

 many either dispute its presence altogether, or assert that 

 if it exists it may be safely employed the same as the 

 sap of Lignum Vitae ; this is, however, by no means 

 certain, as I have found that if it is placed in any 

 damp or imperfectly ventilated situation, it decays 

 much sooner than the heart-wood ; but if used under 

 more favourable circumstances, its durability is very 

 great. 



In connection with this question, a merchant and 

 importer of Greenheart timber said upon one occasion, 

 when we had a parcel under survey, that he was confident 

 a certain log had no sap-wood upon it, for if it had, it 

 would be liable to the attack of a small worm, but that 

 the worm would not touch the heart- wood. The log 

 referred to was accordingly tested by cutting off a thin 

 cross section, and upon examination of the piece, there 

 were found in it several marks or traces of the worm, 

 which had penetrated to the depth of 2 to 3 inches ; 

 the heart-wood, or duramen, had not, however, been 

 touched. The gentleman at once admitted that, with 

 such evidence, he would take it as conclusive that there 

 was sap to the depth of 3 inches on the log, but that its 

 appearance had entirely deceived him. 



