XII. W. E. COOK. 
20 is quartz tailings. Nos. 21 to 25 are samples of river 
sands, and Nos. 26 to 28 hill sands, which still show how 
much injury may be done to the mortar by washing the 
sand. Nos. 29 and 30 are sea beach sands. Nos. 31 to 34 
are the only river sands which have been, and are being, 
used on the Watts’ River Aqueduct. These samples are 
interesting as showing in No. 31, one which it would have 
been detrimental to wash, No. 32 one in which it did not 
make any difference to the result if the sand were washed 
or not, and Nos. 33 and 34 are samples of sand for the 
washing of which a large steam plant was erected. Nos. 
do aud 36 are the only exceptions I have had of hill sands 
requiring washing. Nos. 37 to 39 are decomposed granite, 
and a more unpromising looking sample one can hardly find, 
yet it stood when washed a fair strain, whilst Nos. 40 to 
43 show how very worthless some sands are, although 
appearing good to the eye. In general the hill sands are, 
as is apparent, much superior to the river sand. The red 
jine in the diagram represents the standard (75tbs. per 
Square inch) that was adopted for the sand to come up to, 
in order to be accepted, all below being rejected. 
From the diagram it will be seen that of 8 tests with hill 
sands two only, viz., 35 and 36, showed improvement by 
washing. When the river sand tests are examined, it is 
found that in 13 cases out of 19 where the samples were 
tested, both washed and unwashed, the unwashed sands 
gave better results than the washed sands. This does 
not bear out Mr. Oliver’s statement, that “in general all 
river sands require washing.”’ 
These experiments show clearly that in general washing 
hill sands deteriorates them, and that in some cases the 
same is the case with river sands. Attention might also 
be drawn to the fact that of 4 samples of Sandridge sand, 
the coarsest gave by far the best result. 
