RICHARDS, — SOLID SOLUTIONS. 383 



(o) The nature of the groups which are occluded iu the cases of iron, 

 chromium, aud aluminum is not yet determined, but they are probably 

 basic iu nature, and identical with the complexes of Kecoura and 

 Whitney. 



Harvard University, Cabibridge, Mass., 

 February 2, 1900. 



