1916] THE GROWTH OF ETCH-FIGURES 257 
came more strikingly evident. The reflections from figure-faces are 
then seen to differ in a marked manner from those which would be 
obtained from a series of normal crystal faces. They consist of a number 
of light-paths radiating from a common centre. In some cases the rays 
are long and join in a small central patch of light, and in others it is 
the centre that is well-defined, and the light-paths are short and indis- 
tinct. 
In order to make a careful study of these phenomena as exemplified 
by diopside, a crystal which had been exposed to a 50% solution of 
