It would seem, therefore, that the validity of Einstein’s Brownian-movement equation had been pretty thoroughly established in gases. In liquids too it has recently been subjected to much more precise test than had formerly been attained. Nordlund,[93] in 1914, using minute mercury particles in water and assuming Stokes’s Law of fall and Einstein’s equations, obtained
. While in 1915 Westgren at Stockholm[94] by a very large number of measurements on colloidal gold, silver, and selenium particles, of diameter from 65
to 130
(
), obtained a result which he thinks is correct to one-half of 1 per cent, this value is
