164 Lieut. J. B. Scrivenor — Origin of Clays and 



anything that supports the explanation put forward above. In 

 every case the bedding is clearly preserved, although the rocks 

 are soft. 



Another possibility might be put forward. When some limestone 

 dissolves away a residual mass of insoluble impurities is left behind. 

 Are the clays and boulder-clays simply the residue left behind as the 

 limestone surface was lowered by solution ? If the Kinta limestone 

 were impure this would account for much, but it would not account 

 for the beds with boulders of granite at Gopeng, and I think that 

 a fatal objection to it is that analysis shows the limestone to be an 

 exceptionally pure carbonate rock. Analyses by Mr. C. Salter of 

 two typical specimens of limestone from near Mengiembu gave the 

 following results : — 



SiOa 



AI2O3 



FeaOa 



MgO 



CaO 



CO2 



100-71 100-98 



At the Tekka granite-junction the veins containing fluorite and 

 the blue tourmaline veins suggest association with limestone ; the 

 fluorite because it is calcium fluoride, the tourmaline because similar 

 tourmaline has been found in limestone on the Tekka Ltd. mine and 

 at Siputeh. But I do not think that anyone who has examined the 

 crystalline limestone and the clay at Tekka could conclude that the 

 latter is the residual impurity of the former. If it were, and if 

 the veins were originally encased in limestone, the latter could not 

 possibly retain their course as veins now, because the diminution of 

 bulk of the containing rock would be enormous. 



Finally, it may be said in favour of the clays and boulder-clays 

 having been deposited as clays and boulder-clays that in Sarawak 

 there have been exposed, in the gold-mines of Bau and Bidi, jnany 

 sections of shale over limestone, and generally, as far as I can 

 recollect, the bedding in the latter was distinctly preserved, although 

 the limestone had been attacked by water and carved into irregular 

 pinnacles just as much as in Kinta. 



If the clays and boulder-clays were laid down as such the only 

 explanation of their peculiarities that can be adduced is that they 

 are of glacial origin. The evidence against this and against the 

 deposits being in their original condition must now be given. 



The first objection to the glacial theory is that on the west side of 

 the valley boulders of difierent rocks are not mixed up as they 

 usually are in boulder-clay. The tourmaline-corundum rocks are 

 not mixed with boulders of granitic rocks. On the Siputeh Ltd. 

 property I have not seen any tourmaline-corundum rocks, although 

 in the Fusing Bharu mine they were very abundant, and have also 

 been seen at Siak. On the other hand, in the Siputeh mine are 

 abundant boulders of tourmalinized quartzite with tin- ore and 



