Note 107 — Chapter III · METHODS OF MEASUREMENT.

It is very desirable that care should be taken not to release large quantities of the radium emanation inside a laboratory. This emanation has a slow rate of decay and is carried by currents of air throughout the whole building and finally leaves behind an active deposit of very slow rate of change (see chapter XI.). Eve (Nature, March 16, 1905) has drawn attention to the difficulty of making refined radio-active measurements under such conditions.