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Dilatation of sand
The dilatation of sand is well shown by india-rubber balloons, which can be expanded by the mouth, these afford an almost transparent
Fig. 15.
envelope. Taking one which holds six pints of sand and water, closed without air, there being more water than will fill the interstices at maximum density, but not enough to allow the full extension of the interstices. When standing on a table the elasticity of the envelope gives it a
