4a 
May 27, 1867. 
Professor CHALLIS (VICE-PRESIDENT) in the Chair. 
The following were elected Honorary Members of the 
Society : 
MM. EHRENBERG, 
PONCELET, 
PLUCKER, 
AGASSIZ, 
»  QUETELET, 
Dr DAUBENY, 
Dr Topp, 
Mr STEPHEN SMITH, 
Mr Max MULLER. 
(1) On a New Method of maintaining the Oscillations 
of a Pendulum. By W. H. Miturr, M.A., For. 
Sec. R.S., Professor of Mineralogy in the Uni- 
versity of Cambridge. 
2) 
ted 
) 
Professor Challis expressed his admiration of Professor 
Miller’s contrivance, and described the practical difficulties which 
he had experienced with ordinary pendulums at the Obser- 
vatory. 
(2) On the Crystallographic Method of Grassmann, and 
on its employment in the investigation of the general 
geometric properties of Crystals. By Prorussor 
MILLER. 
INTRODUCTION. 
1. The law to which the mutual inclinations of the faces 
and cleavage planes of a crystal are subject, as enunciated by a 
large majority of the writers on Crystallography, is essentially 
embodied in the following statement :— 
