AREA OF WATERWAYS, ETC. 629 



a proper and scientific basis ; and it is felt that this Association is 

 the proper and national medium through which to approach and 

 prevail upon the authorities to initiate the work. 



2.— THE SAND BLAST TEST APPARATUS FOR TESTING THE 

 WEARING QUALITIES OF TIMBERS WHEN USED IN FLOORS 

 OR FOR STREET PAVING. 

 By PROFESSOR WARREN and Mr. J. MacD. ROYLE. B.E., Demonstrator in Engineertng. 



(abstract) 



The experiments described in this paper consist of a special appa- 

 ratus designed to produce a jet of sand by means of steam pressure 

 at 42 pounds per square inch. The sand was of standard quality, 

 having grains of uniform size regulated by passing it through 

 sieves of a definite mesh. The apparatus is so arranged that no 

 particle of sand is used more than once, and after impinging on the 

 specimen it collects in a vessel and is thrown away. The specimen 

 of timber is fixed in the apparatus, and the sand is allowed to 

 impinge upon it for a definite time, generally from two to five 

 minutes, according to the hardness of the timber, the results being 

 afterwards reduced to the equivalent effect produced in two minutes. 

 The specimens were prepared of uniform dimensions, and were 

 tested in three directions as follows : — 



A. — Parallel to the axis of the tree on the end grain, as in 

 street paving. 



B. — Perpendicular to the annual rings. 



C. — Tangential to the annual rings. 



The hardness of the timber in regard to resistance to wear is 

 greatest when tested as in A, and least when tested as in C. In the 

 case of blackbutt from the North Coast the hardness in the direction 



A, as used in street paving, is three times as great as in the direction 



B, as used in flooring boards, and 4.7 times as great as in the direc- 

 tion C. This ratio differs slightly with other timbers, and the 

 order of hardness compared in each of the three directions is not 

 the same, but the table giving the order of combined hardness in 

 the three directions A, B and C places woollybutt (South Coast) 

 at the top, followed by turpentine, spotted gum and grey box — 

 all from the South Coast. Grey ironbark from the North Coast 

 comes fifth, South Coast blackbutt sixth, and North Coast black- 

 butt thirteenth ; North Coast tallow-wood is fourteenth, and 

 colonial teak (North Coast) sixteenth. 



Tests of exceptionally well-seasoned blocks tested as in A 

 showed that spotted gum would wear better than blackbutt in 

 street paving, and that either were superior to tallow-wood ; 

 whereas jarrah was not even as good as tallow- wood. The exhibit 

 of tested specimens and the numerous diagrams and tables show 

 very clearly the resisting power of New South Wales timbers to 

 wear and abrasion- 



