THE TIMBERS OF NEW SOUTH WALES. 199 



the outer grain, owing to the continued jarring caused by the adze 

 or axe in the timber squarer's hands in dressing the piece to the 

 required size. I experimented to satisfy myself on this point 

 recently, with the result as follows : Two pieces of ironbark, 

 twenty feet long, fourteen by ten inches, sawn, and to my know- 

 ledge from the same tree, were submitted to me ; both these pieces 

 started to shell and crack. One piece I used in the work, the 

 other I had adzed-dressed down to size of fourteen by seven inches 

 and then planed. The smaller piece although three inches nearer 

 the heart remained free from blemish, while the larger piece con- 

 tinued to split and crack for some time afterwards. I look upon 

 this point as one of importance, hence my referring to it. 



Hardwoods Painted or Tarred. 



Our timbers contain natural juices to a more or less degree (no 

 matter what season of the year the trees are fallen), which gradu- 

 ally exudes from each piece along its face and at the ends while 

 drying. It is a common practice among architects and engineers 

 in the erection of buildings and public works to have the unseasoned 

 timber painted or tarred, as the case may be, as quickly as possible, 

 to prevent splitting and cracking, a process which not only serves 

 to check the natural process of drying, but worse still, sets up an 

 element of decay inasmuch as the juices are prevented from flow- 

 ing and are transformed from a natural element into an injurious 

 one. No green or unseasoned timber should be tarred until it 

 becomes to some degree dry, while in planed work a coating of oil 

 in lieu of paint will stop the splitting or cracking equally as well, 

 and does not check the flow of the sap. 



How often we see in bridges months after erection the painted 

 members sap- stained through the weak painted places along the 

 face, presenting an unsightly appearance. 



When iron bolts are used, they should always be oiled through- 

 out their length, otherwise the sap when it reaches the iron, pro- 

 duces an iron stain which eventually flows through the bolt hole, 

 and can only be removed by scraping. 



