510 #. H. Davison—Primary Zones of Cornish Lodes. 
far to the north as that the granite is at no great distance below the 
surface, and there is every probability that the copper and tim zones 
occur at workable depths over a large area to the north of the 
present mines in the Camborne-Redruth district. 
: Crowan 
Gwinear. Praze. Beacon. * 
Contact 
altered slate. 
Fig. 2.—Sketch section from Crowan Beacon to Gwinear. 
Gwithian Crowan 
Sands. Pendarves. Beacon. 
Contact 
altered slate. 
Fic. 3.—Sketch section from Crowan Beacon to Gwithian. 
Bridge 
Elvan with 
Sheep granite Carn Nine 
rock. inclusion. Brea. Maidens. 
Fic. 4.—Sketch section from Nine Maidens to Portreath. 
In addition to the vertical zones of the lodes described above, there 
is a variation in the lode contents along the strike. A lode is not 
usually of uniform value throughout its length, but the metallic 
minerals occur in “ shoots ” or “ courses *’ which alternate along the 
lode with areas of low-grade ore of little or no economic value. These 
shoots are not usually vertical, but run diagonally down the lode 
and their exact relationship to their surroundings remains to be 
determined. It seems probable that they are due to variation in the 
country rock, and in the nature of the fissure, and I am at present 
engaged in the collection of data concerning them. 
