I am much oblig’d by your valuable Present of several Tracts which I received thro’ the Hands of our common Friend Sir John Pringle; particularly for that on Fix’d Air, a Subject which of late engages much the Attention of our Philosophers here, and in which no one has more distinguish’d himself than Dr. Priestly, who puts this Letter into your Hands. His Character in the Republick of Letters you must be well acquainted with, and I am sure you will be pleas’d with the Opportunity of conversing with him. I beg your Acceptance of the enclos’d Pamphlet, and am with the greatest Esteem, Sir, Your most obedient and most humble Servant