230 P, DOYLE ON SOME TIN-DEPOSITS OF 
There can be no doubt that these beds have been formed by degra- 
dation of the mountains; these, as has been stated, consist of granitic 
rock, in which the tin-stone associated with iron-ore occurs in veins. 
We still see the processes at work, though in a modified form, by 
which deposits have been spread over large areas during long periods 
of time ; and the rotting trunks of trees, with other remains frequently 
met with in the workings, tend to prove that some of the deposits 
may be properly called “recent.” 
Sections of the mines show that the strata beneath the surface- 
soil consist of alternating bands of sand and dark clay of different 
colours, the latter sometimes being largely present. These strata 
appear to indicate strong current-action. The separate fragments 
in the lowest (or tin-bearing) layer bear clear evidence of the same. 
These fragments are of quartz, felspar, mica, and schorl; and 
among these are occasionally found masses of clay, most of which 
are so friable as to crumble to pieces when touched. In some, particles 
of quartz yet remain projecting from the surface, so as to give it a 
regular striated aspect, from which felspar separates as a white 
powder. Many of the more solid fragments have rounded angles, 
and are evidently derived from veins such as still occur in different 
parts of the country. 
Beneath the tin-bearing stratum is a peculiar white clayey substance 
which becomes friable on drying and is called “‘ Kong tay” by the 
Chinese. This is sometimes yellow, sometimes white or somewhat 
bluish. It consists of kaolin, sometimes mixed with fine quartz- 
sand, and is a decomposition-product of felspar. The kong has 
been bored to a depth of 20 feet ; but nothing except this “‘ porcelain 
clay,” mixed with more or less quartz-sand, has been found. 
Opinions differ as to whether this clay invariably underlies the 
stanniferous deposits. In the Larnt district there is little doubt 
that it does generally, the only exception to the rule being where the 
tin-stratum rests on sandstone, which, however, some have thought 
to be only the same clay with a large admixture of the quartz-sand 
already mentioned. 
The following are sections of stream-deposits in different localities 
and will give a very fair general idea of the district :— 
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ME OUNN Toec cannes seneenasenaeanatuteceremeceace ce 
Sam Gy aaech aarca te edac tices sunita teane era cmadeaeene 
Bluishclay Kay sti cise pees eee 
Damkishy lay: ys sehasqesinswcnseuen suas 
> 09 Go HR RE 
SCORCOWE 
| 
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(io) 
6 
106, 
(Mouldesoilt yes: aveauueso: na rencneaett cs 3 0 
Clay varying from dark yellow to pale grey 12 0 
inehtrerayellyacritivmece ccc eset 3 0 
Siratuny With Ore. wasesicteqenvearaamateem. 6 0 
I) 
He 
(=) 
