PHILOSOPHIC A L 
A N S A C T I O N 
OF THE 
11 O Y A L S O 0 I E T Y 
OF 
LONDON, 
FOR THE YEAR MDCCCLXXX. 
VOL. 171.—PART III. 
LONDON: 
PRINTED BY HARRISON AND SONS, ST. MARTINS LANE, W.O., 
|)rmt.ers hr (Drbinarg to fur ^lajcstg. 
M DCCCLXXXI. 
