Professor Lehmann has succeeded, in fact, in obtaining with certain organic compounds-- oleate of potassium, for instance--under certain conditions some peculiar states to which he has given the name of semi-fluid and liquid crystals.

These singular phenomena can only be observed and studied by means of a microscope, and the Carlsruhe Professor had to devise an ingenious apparatus which enabled him to bring the preparation at the required temperature on to the very plate of the microscope.
It is thus made evident that these bodies act on polarized light in the manner of a crystal.

Those that M.Lehmann terms semi-liquid still present traces of polyhedric delimitation, but with the peaks and angles rounded by surface-tension, while the others tend to a strictly spherical form.

The optical examination of the first-named bodies is very difficult, because appearances may be produced which are due to the phenomena of refraction and imitate those of polarization.

For the other kind, which are often as mobile as water, the fact that they polarize light is absolutely unquestionable.
Unfortunately, all these liquids are turbid, and it may be objected that they are not homogeneous.