M. Dufour has shown that an imponderable quantity of a substance
can be crystallised; and that the crystals so obtained are quite
characteristic of the substances, as of sugar, chloride of sodium,
arsenic, and mercury. This process may be extremely valuable to the
mineralogist and toxicologist when the substance for examination is too
small to be submitted to tests. By aid of the microscope, also, shells
are measured to the thousandth part of an inch.