642 



C. LE NEVE FOSTER ON THE GREAT FLAT LODE 



rarely seen during the workings on the lode ; but their presence is 

 well ascertained by crosscuts and shafts in these enclosing rocks or 

 country. The crosscuts have further proved that there is no wall, 

 or definite plane of division, between the greyback and the granite, 

 any more than there is between the greyback and the lode ; nor is 

 there any straight line of demarcation between the killas and the 

 ca])el. 



There may be a much greater quantity of carpel above the lode 

 than is shown in my sketch ; in fact the crosscut south at the 80- 

 fathoms level shows that it extends for many fathoms, whilst the 

 killas that is eventually met with is converted into mica- schist. 



As may be naturally sujjposed, the lode varies a great deal in cha- 

 racter. Sometimes the tin-bearing rock, or lode, is above instead of 

 being below the leader ; thus, in some stopes above the 110-fathoms 

 level, I saw the following section (fig. 2) : — 



Tig. 2. — Section at Wheal Uny, above the 110-fathoms Level. 



N. S. 



S3 C & A HUB E 



Sct3fij.ua kg itush,=. j. foot. " ' 

 o a -i c 8 w ic Feet 



A. Leader, 2 to 10 inches wide, a breccia of fragments of chloritic slate cemented 

 by iron-pyrites and quartz. 



B B. Lode, a very fine-grained or compact stanniferous schorl-rock, with strings 

 and spots of quartz and cassiterite, and numerous veins of quartz enclosing 

 fragments of schorl-rock cemented by iron-pyrites. It is traversed by a 

 clay-vein (flucari) H, containing a little quartz and iron-pyrites. 



B'. Lode, compact schorl-rock, with spots and little veins of quartz and tin- 

 stone, 4 inches thick, under the leader. 



C. Capel, compact schorl-rock, with spots and veins of quartz, containing very 



little tin, 2 feet thick. 



D. Black granite, or greyback, a schorl-rock with large grains of quartz in a 



compact black matrix, probably about 6 feet thick.- 



E. Ca-pel. There is a difference between the capels C and E ; the latter shows 



the component minerals arranged in layers, which are signs of original 

 stratification ; the former does not. F. Killas. 



G-. Granite. Neither of these is actually seen in the section underground. 



On looking at the longitudinal section of Wheal Uny it does not 

 seem possible to make out any dip of the bunches of tin- ore; in 

 fact I am informed that no part of the lode is absolutely barren, 

 the rock near the leader will always contain at least ^ per cent, tin- 

 ore {black tin). 



