io6 THE TIMBERS OF THE WORLD 



pavement with varying results, some being unsurpassed in excellence, 

 while others were somewhat discouraging. The causes for these variations 

 can, however, in most cases be ascertained. Perhaps the most important 

 factor is the question of the pavement foundation, while the time which 

 is allowed for carrying out the work has also some bearing on the result. 

 Unfortunately the laying of pavement is in most cases much too hurried, 

 and probably too httle time is allowed both for making a proper 

 foundation and for seeing that this is sufficiently settled before proceeding 

 with the work. It is also doubtful if engineers have even yet specified 

 either sufficient solidity, or enough regularity for the foundation of a 

 hardwood pavement. The force which the jarrah block has to sustain 

 from the heavy weights continually striking the surface, is transferred to 

 the foundation in a quite different manner from that which takes place 

 with a softwood block, which is much more resilient and consequently 

 acts as a kind of buffer. Possibly a medium between the concrete and the 

 block to take this strain would make a considerable difference. As it is, 

 any weakness which develops causes the foundation to give way and 

 brings about the beginning of the " holey " places which characterises 

 hardwood pavements. Immediately one block sinks even a httle below 

 the level of those surrounding it, every wheel bumps on the edges and 

 increases the strain enormously, and this again enlarges the area and 

 deepens the hole. Again, if the foundation be carelessly laid, or on 

 account of urgency an insufficient time is allowed for it to set completely, 

 the same trouble ensues. A careful inquiry into the question of founda- 

 tions for hardwood pavements should be instituted, as there is no doubt 

 that, as the cost of labour is nearly as much for laying the softwood as 

 for the hardwood, a great saving of expense could be assured if this 

 difficulty was overcome. Even in the present circimistances a 5-inch 

 jarrah block pavement has, since 1906, withstood the exceedingly heavy 

 traffic in the Euston Road, London, with fairly good results, and has 

 therefore now (1919) sustained thirteen years of continual use. 



Some of these blocks were taken up for repairs this year, and appeared 

 as sound and hard as when they were laid. I had one sawn into i-inch 

 thicknesses and planed, and not only is the wood in splendid condition, 

 but neither manure nor other deposits which it has had to withstand have 

 impregnated the pores, as is so generally found with softwood blocks 

 after a much less time. Again, the Variation of hardness in individual 

 jarrah blocks is much greater than in the case of softwood, so that if 

 only one of the softer kind is surrounded by harder, the same result 

 referred to above occurs. It has been noted that the outer growth of 

 jarrah trees is very much harder and closer than the heart growth, and 

 there is also, of course, a variation in the trees themselves. To guard 

 against this danger it is generally specified that only the harder wood 



