FACTS IN AMERICAN MINING. 75 



The Eureka Mine, Amador County, furnishes some curious and 

 interesting facts, in a measure subversive of certain recognised 

 geological dogmas. It is commonly believed that the yield of gold 

 must decrease in depth; but in this mine the value of the yield 

 for the first thirty feet was only 30s. to 60s. per ton, barely sufficient 

 to pay expenses. Below that level it rose from 56s. to 84s. ; at 

 100 feet it yielded £5 12s., at 200 feet, £7 4s., and at 300 feet it 

 attained a yield of £12 per ton. From this we may learn some 

 important lessons. It shows that we must not apply scientific 

 dogmas in all cases ; that because the surface is poor, the mine 

 must be unworthy of trial or necessarily poor in depth. This 

 mine yielded in one year a profit of £75,000, and has attained a 

 depth of 1,200 feet. It is a noticeable feature that it exists at the 

 junction of slate and greenstone, the latter being hard and com- 

 pact, and forming the hanging wall ; while the footwall is com- 

 posed of a soft argillaceous slate. To the junction of these two 

 formations is ascribed much of the success of this mine, and the 

 continuity of the gold in depth, while the soft character of the 

 footwall has enabled the mining to be conducted at small cost. 

 The opinion that quartz veins grow poorer in desending appears 

 to be unsupported by sufficient evidence, but there are a number 

 of circumstances calculated to lead the superficial observer to that 

 conclusion ; one of these is found in the fact that as the portion 

 of the reef exposed to atmospheric influence gets weathered, it is 

 necessarily accompanied by the degradation of some of the quartz, 

 in most cases leaving the gold ; the capping is therefore not a fair 

 sample of the quartz in the immediate vicinity ; then again, every 

 reef varies in richness in different portions of its length and depth, 

 and a prospector would be most likely to select from the richest 

 portions showing on the surface. Moreover, the gold almost in- 

 variably exists in bunches, shoots, or chimneys, which cut the 

 axis of the vein horizontally, or vertically, at all angles. Not 

 unfrequently the gold will be on one or other of the walls for a 



On the West Coast of New Zealand, a cemented sea-sand of quite a different character 

 is met with and worked for gold : it is conglomerated with iron, and such is its hardness 

 that, though usually removed by the use of a gad, it has frequently to be blasted with powder. 

 It is unmistakeably a sea deposit, being left bare by the receding sea, as the laud has gra- 

 dually risen. It is crushed in the ordinary way, and leaves large dividends, with a yield of 

 only 1 dwt. per ton. The gold occurs in distant leads, parallel to the sea-coast; they vary 

 from 20 to 50 feet in width ; all the rest is barren, in the intervening space between these 

 leads. Their direction is so true that the diggers follow them for miles by compass, fre- 

 quently cutting their way through the bush for considerable distances, to pick up the precise 

 point indicated by the needle, and seldom mark out a claim anywhere outside of the line. 

 Far back from the water's edge there are a series of these leads, all preserving their parallel- 

 ism for miles. The operation known as '-haymaking" consists in collecting the sand thrown 

 up by the spring tides, consisting largely of titaniferous iron, with loose gold visible to the 

 eye, on walking over it. This is removed, and afterwards treated by running through a box. 

 It is a remarkable fact that all the gold leads on the West Coast partake of the same char- 

 acter of parallelism, and are evidently deposited in the same way. It is, however, believed 

 that the gold is originally carried down by the river running at "the back of the range. To 

 show the changes taking place in the level of the land, there may be seen on the West Coast 

 of New Zealand, South of Ilokitika, and nearly half a mile back from the sea, the remains 

 of an old whaling vessel surrounded by thick scrub ; some part of the hull is still in a good 

 state of preservation, and where the mast once stood, now grows one of the mouarchs of 

 the forest. 



