TERRA, &c. 



I AM called upon by command from your lordship, and the council 

 who direct the progress of the Royal Society, to entertain this illustrious 

 assembly with something which, being either deduced from, or leading 

 to, philosophical experiment, may be of real use, and suitable to the 

 design of its institution. 



I am highly sensible as of the honour which is done me, so of the great 

 disadvantages I lie under for want of abilities to carry me through an 

 undertaking of this importance, and before such acute and learned 

 judges ; but I hope my obedience to your commands will cover those 

 defects, for which I can make no other apology. 



There are few here, I presume, who know not upon how innocent and 

 humble a subject I have long since diverted my thoughts ; and, therefore, 

 I hope they will not be displeased, or think it unworthy of their patience, 

 if from their more sublime and noble speculations, (and which do often 

 carry them to converse among the brighter orbs and heavenly bodies,) 

 they descend a while, and fix their eyes upon the earth, which I make 

 the present argument of my Discourse. I had once indeed pitched upon 

 a subject of a somcAvhat more brisk and lively nature ; for what is there 

 in nature so sluggish and dull as earth ? What more spiritual and active 

 than vegetation, and what the earth produces ? But this, as a province 

 becoming a more steady hand and penetrating wit than mine to cultivate, 

 (unless where it transitorily comes in my way to speak of salts and fer- 

 ments,) I leave to those of this learned Society, who have already given 

 such admirable essays of what they will be more able to accomplish upon 

 that useful and curious theme; and, therefore, I beg leave that I may con- 



Volume IL 3 F 



