Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/73

 water, I should agitate it with my hand in all directions, and, when the water became muddy, pour it off and add more to it, holding the gamella with my left-hand, and stirring the gravel with my right, repeating the change of the water, until the earthy particles were dissolved, and the pebbles clean washed. During this agitation, from the peculiar form of the vessel, the heaviest substances in the cascalho would have sunk lowest and remain undisturbed, the surface being in a tenfold degree more exposed to this sort of trituration than the bottom.— Having poured off the clear water and thrown away the stones from the surface, the remainder would require to be carefully examined; the diamonds, if any, being heavier than the pebbles, would be found at the bottom, and may easily be discovered through the medium of water, which gives them an additional lustre, so that they cannot be mis-