202 J. V. DE COQUE. 



grub makes it often difficult to discover the extent of the injurjr 

 to the log. It will sometimes enter a tree from the outside and 

 not finding the timber exactly to its taste will probably bore its 

 way for a few inches and come out again, more often, however, it 

 bores across the grain until it reaches the heart, which it carefully 

 avoids, and continues its course parallel for several feet when it 

 either dies or comes out again. 



The actual hole made is but little injury to the girder, the real 

 danger lies in its touching the heart, exposing it to moisture, 

 which begins at once to cause decay, and rot, which rapidly 

 increases. An experienced hand can detect the rot inside a girder 

 by the sound made with the blow of a hammer, but in ordinary 

 cases when grub holes are to be seen, it is well to bore an auger 

 hole through the heart close to the entrance and along the line. 

 If no rot appears you can rely on the soundness of the piece. I 

 have frequently seen logs quite rotten inside for several feet in 

 length, yet no outward warning except a grub hole. 



Dry limb knobs should always be carefully examined in girders 

 containing heart ; providing no rot shows in or around the knob 

 in the generality of cases the log or piece is sound, but some 

 unprincipled timber getters are experts at plugging what may be 

 a very faulty stick ; a blow with a hammer on the knot will 

 quickly expose plugging, as it will move under the blow. The 

 heart of the ironbark tree is always first to decay. It is better 

 therefore to avoid using heart pieces when possible. 



Grey Gum — Eucalyptus saligna, var. 



This timber must not be confounded with the Blue Gum — 

 E. saligna. It is a remarkably close grained, durable timber, 

 and except as regards strength, (to which it is inferior to ironbark), 

 it makes an admirable substitute, particularly in the erection of 

 large beam bridges. It is very like red ironbark in general 

 appearance, and is often substituted for it. An experienced man 

 can however detect the difference owing to the shortness of grain. 

 A chip of grey gum bent between the fingers will snap instantly. 



