To the Honourable the 
PRESIDENT and FELLOWS 
O F T H E 
Royal College o/'Physicians, ^London. 
Honoured Sirs, 
H E juft Senfe I have of Your great Learning 
and profound Judgment in all the Sciences, and 
my own Ignorance in moft of them, might 
deter me from Prefenting this Trifle, was I not 
encouraged by Your great Goodneis and Willingnels to 
cherifti and give Life to the leaft Spark of Knowledge 
You perceive kindling in any one, tho* of inferior Rank 5 
which Benevolence in You removes that Fear, that 
otherwife would forbid my Approach. This Work hath, 
indeed, receiv’d its very Being from your Smiles 5 for the 
favourable Reception my firft Eflays in this Way, fome- 
time ago prefented to the College met with, hath 
A 2 encouraged 
