The more common form of alluvial gold is as grains, or scales, or dust, varying in size from that of ordinary gunpowder to a minuteness that is invisible to the naked eye. Sometimes indeed the particles are so small that they are known as 'paint' gold, forming a scarcely perceptible coating on fragments of rock. When the gold is very fine or in very thin scales, much of it is lost in the ordinary processes for treating gravels, by reason of the fact that it will actually float on water for a considerable distance. From what has been already said it will be evident that gold-mining must be an industry presenting several distinct phases. These may be classed as alluvial mining, vein-mining, and the treatment of auriferous ores. In alluvial mining natural agencies, such as frost, rain, &c., have, in the course of centuries, performed the arduous tasks of breaking up the matrix which held the gold, and washing away much of the valueless material, leaving the gold concentrated into a limited area by virtue of its great specific gravity. Hence it is never safe to assume that the portion of the veins remaining as such will yield anything like so great an equivalent of gold as the alluvials formed from the portion which has been disintegrated. As water has been the chief (but not the only) agent in distributing the gold and gravel constituting alluvial diggings or placers, the banks and beds of running streams in the neighbourhood of auriferous veins are likely spots for the prospector, who finds in the flowing water of the stream the means of separating the heavy grains of gold from the much lighter particles of rock, sand, and mud. Often the brook is made to yield the gold it transports by the simple expedient of placing in it obstacles which will arrest the gold without obstructing the lighter matters. Jason's golden fleece was probably a sheepskin which had been pegged down in the current of the Phasis till a quantity of gold grains had become entangled among the wool. To this day the same practice is followed with ox-hides in Brazil, and with sheepskins in Ladakh, Savoy, and Hungary. This may be deemed the simplest form of 'alluvial mining.' If the gold deposited in holes and behind bars in the bed of the stream is to be recovered, greater preparations are needed. Either the river-bed must be dredged by floating dredgers, worked by the stream or otherwise; or the gravel must be dug out for washing while the bed is left dry in hot weather; or the river must be diverted into another channel (natural or artificial) whilst its bed is being stripped. The first-named method is best adapted to large volumes of water, but probably is least productive of gold, passing over much that is buried in crevices in the solid bed-rock. The second plan is applicable only to small streams, and entails much labour. The third is most efficient, but very liable to serious interference by floods, which entail a heavy loss of plant.