TO THE 
Righe Honourable 
WILLIAM 
Lord Vi-Count BROUNCKER:: 
THE : 
PRESIDENT: 
ANDTO THE 
Council and Fellows 
O RITHE 
ROYAL SOCIETY. 
MY LORD, 
HE Commands I received from Your Lord. 
Jbip, and the Royal Society, To profecute 
the SubjeS treated of in the Two former Books; 
have produced This which follows. And I 
humbly fubmit the fame to Tour Lordfhips Judg- 
2 ment: 
