Dr. J. E. Wolff delivered a lecture last evening in Boylston Hall before the Boylston Chemical Club. He took as his subject "The Molecular Structure of Crystals." He said in part:

Crystals represent collections of solid matter, bounded by perfect planes. These planes are peculiar in that they take so many different angles with each other. Cohesion exists in two forms, cleavage and hardness.

It is supposed that crystals are made up of crystal Molecules, arranged with perfect regularity and composed of a large number of chemical molecules. In all parallel planes there is the same distribution of molecules. The closer they are together in a plane, the greater is the distance apart of two similar planes. The farther apart two planes are, the less is their cohesion. Only certain planes occur in Nature. The lecturer illustrated his talk by various specimens, models, etc.