X 
PREFACE. 
recommends the ftudy of them, yet he 
makes ufe of motives that have no relation 
to the common purpofes of life. 
When Kepler, from a blind and flrong 
impulfe merely to find analogies in nature, 
difcovered that famous one between the 
diftances of the feveral planets from the 
fun, and the periods in which they com- 
' pleat their revolutions ; of what importance 
was it to him or to the world ? 
Again ; when Galileo, pufhed on by the 
fame irrefifiible curiofity, found out the law 
by which bodies fall to the earth, did he 
or could he forefee that any good would 
come from his ingenious theorems, or was 
any immediate ufe made of them ? 
Yet had not the Greeks pufhed their ah- 
ftrad fpeculations fo far 5 had not Kepler 
and Galileo made the above mentioned dis- 
coveries 5 we never could have feen the 
greateft work that ever came from the 
hands of man. Every one will guefs that 
i mean Sir Ifaac Newton’s Principia. 
Some obfeure perfon, whofe name is not 
fo much as known, diverting ..himfelf idly 
as 
