Being diffident of my own Performance, and desirous it should stand or fall by the Opinion of the Best of Judges, was the Motive that induced me to make my Application to that very Learned, truly Judicious and commendably Curious Person to whom it’s dedicated: At the same time determining, that if he approv’d of it, I would publish it; and if he disapprov’d, that I would burn it. But it happily meeting his Approbation, it now makes its Appearance in Print: Tho’ I must in Justice to him acknowledge, it could not have so done so soon, nor with such Embellishments, had he not only forwarded the Impression, but directed and order’d the Copper-plate. As it has not only his Approbation, but also, by his introducing it, the unanimous Concurrent Approbation of (those great Encouragers of things useful) the Royal Society; I hope it will not fail of meeting a kind Reception from the Inhabitants in and about this Metropolis; by whom, as such a Treatise, &c. was most wanted, for their Benefit and Ease it was at first chiefly design’d.

Tho’ with such Helps as it now has, I am not without Hopes that it may extend its Qualities to distant infected Places.

I should think it a Duty Incumbent on me, and would wait on the Venerable Members of the aforesaid Society, present when my Manuscript was read, personally to return them my Thanks for the Honours conferr’d on me. But as the Names and Places of Abode of most are unknown to me, I humbly beg they will accept this Acknowledgement of them, by their

Obliged and Obedient Servant,
JOHN SOUTHALL.