176 HENRY G. SMITH. 



around Sydney, when they are seen under the microscope, would 

 have been obtained. The plates do not break up irregularly in 

 any instance that I can discover, but always in the angular con- 

 dition which these cleavages give. 



This, it must be admitted is a very unnatural method ; but, I 

 am able to show the process going on purely in a natural manner. 

 In the coarse sandstone of the same quarry from which I obtained 

 the Kaolinite, an almost pure white powdery looking substance is 

 filling up the interstices around the grains of quartz. I took a 

 portion of this and examined it under the microscope, and I found 

 it to consist of the same identical plates and crystals ; the crystals 

 are few in number, but it consists largely of the plates, and these 

 plates in the majority of instances show the cleavages very dis- 

 tinctly, most of them having portions removed from their sides, 

 but always broken along these characteristic cleavage planes. 



I also found a beautiful example of a plate of a crystal breaking 

 up in this manner, in the clay from Cronulla Beach, Port Hacking, 

 near Sydney (Plate xxiii., fig. 3.), so that we have been able to 

 trace the Kaolinite through three stages ; the crystallized, the 

 crystallized intermediate, and the clay. 



It is not to be supposed that the Kaolinite that surrounds these 

 particles of quartz, cementing as it were the whole together, and 

 which must be in enormous quantities, distributed over a large 

 area, is the only material of this kind to be found in this deposit, 

 and the matter is one worthy of further inquiry. 



Whether the deposits of clay in the immediate neighbourhood 

 of Sydney, and throughout the Hawkesbury deposits were derived 

 originally from the decomposition of felspar is not certain ; but 

 that the Kaolinite that forms the subject of this paper, and the 

 clay of these deposits are somewhat identical I am convinced ; 

 the evidence so far clearly pointing to these deposits being origin- 

 ally derived from the same material as surrounds the grains of 

 sand as spoken of above. The analyses of this Kaolinite gave 

 about *5 per cent, of magnesia, but no lime. The following three 



