Brownian Movements.

Brownian Movements. When small solid particles—e.g. of gamboge—suspended in water are viewed through the microscope, they are seen to be in incessant vibratory motion. The same movements are also manifested by microscopic germs, but are easily distinguished from those proper to the active state of these, there being no motion of translation in the former case. This observation was first made by the botanist, Robert Brown, whence the name. Its physical cause is somewhat obscure, but the late W. Stanley Jevons showed that these movements (for which he proposed the name diapedesis) varied greatly in proportion as the surface tension of the fluid was modified by the addition of other substances in solution. Soap greatly increases the amplitude of these vibrations, hence, according to Jevons, we have an at least partial explanation of the facility with which it detaches foreign particles.