72 POPULAR SCIENCE MONTHLY 



alone for use in this branch of business, and more than 200,000 miles 

 in all the gold-producing states of America. 



Placer gravel varies in value. The unit of quantity is a cubic 

 yard. In the early days of a new field the ground must carry at least 

 $1 per cubic yard to be attractive to the individual miner or small 

 capitalist. Later, under consolidation and extensive operation, plenty 

 of money can be made out of material carrying fifteen cents per yard, 

 if the physical conditions surrounding the operation are good; that is, 

 plenty of water available and a good dump. At a number of places 

 in the west and in New Zealand good profits are being made from 

 ground carrying much less than fifteen cents per yard. 



The business of vein or reef mining is a very much more elaborate 

 and complicated affair. The lodes or veins of gold-bearing quartz that 

 nature has distributed in certain localities in the rocky crust of the 

 earth are from a few hundred to a few thousand feet in length, so far 

 as their outcrop at the surface is concerned, and from a few inches to 

 a dozen feet or more in width. They extend downward no one knows 

 how far, for as yet the deepest explorations made on any one of them 

 have revealed no termination, though at several shafts in America, 

 Australia and South Africa explorations have been pushed to depths 

 of over 3,000 feet. 



But the quartz of the vein changes continually in value. Here 

 there may be but a trace of the precious metal, while a few feet or 

 yards away a ton may contain as much as $50 worth. Generally, how- 

 ever, the gold is dispersed throughout the vein in patches called " ore 

 shoots," so that certain areas are clearly payable and others not. This 

 is wholly a relative term, depending upon the width of the quartz, its 

 hardness, the nature and condition of the walls, the presence or absence 

 of water, the price of labor, of explosives and of supplies in general, 

 the cost of power for hoisting, pumping and milling, etc. In Mexico, 

 America and Canada money can generally be made on a vein of a width 

 of five feet, that will yield gold to the extent of $5 per ton, and in a 

 number of instances, where the vein is larger, ore worth much less is 

 yielding handsome dividends. Thus, the Homestake mine in South 

 Dakota is paying magnificently on ore that produces on an average 

 about $3.50 per ton, while the Treadwell mine at Juneau, Alaska, is 

 doing finely on $1.50 rock. On the other hand, in Kalgoorlie, the 

 great Australian gold district, where the veins are comparatively nar- 

 row but rich, and all working expenses high by reason of the desert 

 character of the country, the costs connected with mining and milling 

 rarely are less than $7.50 per ton, and in South Africa, where labor 

 has been poor, company management expenses abnormally large, and 

 the payable reef less than twenty inches thick, costs will average even 

 a little more than in Australia. 



Now that, at last, after centuries of irregular and haphazard pro- 



