28o POPULAR SCIENCE MONTHLY 



take out from sand and pebbles diamonds smaller than a pin's head, 

 monds and carbons escape them. This in part accounts for the reason 

 why large diamonds and carbons are frequently found in gravel already 

 washed and picked over. I have heard of places which have been 

 washed for the fourth time and paid, though doubtless in some of these 

 instances the later finds were due to disintegration of conglomerate 

 which yielded up stones heretofore inaccessible. 



The limit of a good man is to concentrate and pick over a cubic 

 yard of cascalho per clay, but this presupposes that the cascalho is 

 easy of access and that the water is near at hand. If the cascalho has 

 to be taken from the cracks, crevices, caves, etc., and with the present 

 methods of mining those are the only places with virgin material 

 which are accessible, it is accumulated very slowly. When it is re- 

 membered that at the South Africa mines there is worked over 192,000 

 cubic feet per day, it can readily be seen why the output of Brazil 

 with its few thousand of hand-workers sinks into insignificance, if 

 indeed the diamonds are in Brazil to extract. 



The 'mines of Minas Geraes have been worked regularly since their 

 discovery, chiefly by hand methods until during the last ten years when 

 some machinery has been installed to aid in the separation of the 

 diamond-producing gravel from the clay and sand and later on in 

 partly sorting the gravel prior to the final clean-up which is always 

 by hand process. In Bahia a little machinery consisting of a few 

 pumps, a gravel sorter and a so-called automatic separator, which does 

 not separate, has been installed at Salobro, but it is being allowed to 

 rust out, work at present being done by hand entirely ignoring the 

 machinery. The only other machinery in the great Bahia district con- 

 sists of a few pumps mounted by an English company on the Sao Jose 

 river. This company has machinery in transit for mounting a small 

 electro-hydraulic plant, but will still leave the clean-up to hand process 

 instead of adopting the automatic table in use at South Africa. 



The diamondiferous lands of Bahia are owned by the state and 

 leased either as small claims or large parcels to parties or companies 

 desiring to work them. About all of the known areas capable of work 

 with groups without machinery have been preempted. The nature of 

 the work already done has been such that many productive areas have 

 been covered with tailings. The river beds and other productive sec- 

 tions which will necessitate machinery are still awaiting exploitation. 



