The supplement to a small treatise called Salt-water sweetned shewing the great advantages both by sea and land, of sea-water made fresh. Together with the Honourable Mr. Boyle's letter, and the approbation of the Colledge of Physicians, of the wholsomness of this water. And also the conditions on which the patentees and others concern'd, do intend to contract with such as shall please to deal with them for the use of his invention.

A LETTER of Mr. BOYLE's to the Learned Dr. JOHN BEALE, Fellow of the Royal So∣ciety, concerning Fresh-water made out of Sea-water: Printed at the desire of the Patentees.

SIR,

TO give you a short Account (suitable to the little time I have to do it in,) of the Transaction, which I suppose must have given the rise to the Mention made of my Name in the publick Gazette,: I must inform you, that one of my nearest Relations, (Captain Fitz-Gerald,) and some other Worthy Gentlemen, having ac∣quainted his Majesty, that They had an Invention for making Sea-water sweet and wholsom in great quantity, and with small Charge, and that I had examin'd, and did approve the Water so prepar'd; His Majesty was pleas'd with very Gracious Ex∣pressions, to command Me to attend him with a further and more particular Information. Ha∣ving readily obey'd this Order, and been made ac∣quainted with the Objections the King thought fit to make against the Practicableness of the Inven∣tion; which, (tho a private Man had urg'd them,) I should think the most Judicious that have been fram'd against it; I humbly presented to him, that I look't upon this Invention as Comprizing two differing things; a Mechanical part, which related to the Engine it self, and the use of it a Ship-board▪ and a Physical part which 〈◊〉〈◊〉

the Potableness and Wholsomness of the Liquour. About the former of these I did not pretend to clear the Difficulties, especially such strong ones, as His Majesty had propos'd; but left it to the Paten∣tees to give him Satisfaction, which they were in a readiness to offer. But as to the Wholsomness of the prepar'd Water, I had made some Tryals upon the Liquour, which gave me no just Grounds of su∣specting it to be unwholsom, but several Motives to believe it well condition'd, and of great use to Na∣vigators, and not to them only. And having here∣upon briefly acquainted His Majesty with the chief Tryals I had made to examin this Sweetned Wa∣ter, He was pleas'd to look upon them as Satisfacto∣ry, and vouchsafed on that occasion to Discourse as a Virtuoso, of the Sea and Brackish-waters, and gave me some new, as well instructive Observations about them: and in conclusion, dismiss'd the Patentees with a Gracious Promise of his Royal Protection, and peculiar Favour.

To this short Narrative it now remains, that I briefly Subjoyn the chief things that perswaded me of the Salubrity of this Water, (whence may be justly and easily inferr'd, the Ʋtility the Publick may receive by a cheap and easie way of preparing it.) First, then I consider'd that almost all the Rain-water that falls from the Clouds on the Main Oce∣an, and which (except perhaps in very few Places in Torrid Climates) is unquestionably receiv'd as wholsom, must be afforded by the Sea, and conse∣quently

be but Sea-water freed from its Salt, (ac∣cording to the famous Motto, Redit Agmine dulci.) Next I found, (as his Majesty himself had done,) that the Liquour was well tasted, and without any sensible Brackishness; and some of it continued for between 4 or 5 Months in a large Christal Bottle, that I purposely kept unstopt, and for the most part in a South Window, where it neither did, nor probably in a long time, will putrifie, or so much as appear troubled or less transparent; during which time, it was with Approbation tasted and smell'd by several Learned Physicians of the famous Colledge of London. Thirdly, I found it laver very well, which most Pump-waters, and many o∣thers that have some little (tho unperceiv'd) com∣mon Salt in them, will not do. Fourthly, this Wa∣ter will boyl Pease tender, which amongst Sea∣men is one of the principal signs of good Water. Fifthly, In very good Ballances, with an Instrument that I purposely caus'd to be made for the nice weighing of Liquours, I found this Water far less heavy than one would expect; for if it differ'd at all in weight from the like quantity of undistill'd Water, (I speak with an If, because it is far more difficult to be exact in such nice Tryals, than the unpractic'd will imagine) the difference was not considerable, being but one part in 400, and that dif∣ference is very small in comparison of that which Navigators and learned Authors relate to be ob∣servable in natural Waters, all of them good 〈◊〉〈◊〉

potable: I might tell you on this Occasion, that the last Great Duke of Tuscany, who was an Emi∣nent Virtuoso, and the Patron of the celebrated Academy of the Lyncean Philosophers, is af∣firm'd, among other prudent Courses that he took for his Health, whereof he was very Sollicitous, to have constantly made use of distill'd Water, when he us'd any Water, for his own Drinking. And I could add other things favourable enough to the Patentees Water, if Haste, and perhaps Discre∣tion too, did not oblige me to leave them yet un∣mention'd, that I might now have time to say some∣what of the main thing of all that convinced me of the Saltlessness of the Water I speak of. I consi∣der'd then, Sixthly, that the thing that was aim'd at by those ingenious men, that at differing times, and in several Countries have attempted to make Sea-water sweet, and the thing that was requir'd by proposing Recompences, or otherwise to encou∣rage the Makers of such Attempts, was to free the Sea-water from the Brackishness without any noxi∣ous Additament: so that on all sides it was taken for granted, that the only thing that kept the Sea-wa¦ter from being safely Potable, was its Brackishness From which reflection it was natural for Me to infer a Conclusion very favourable to our prepar'd Water. For having long since written a short Dis∣course of the Saltness of the Sea; I had been in dustrious to devise ways of comparing Waters 〈…〉〈…〉. And by these I found th••

Patentees water to be more free from Common-salt, than Waters that are usually drunk here in London, of which I remember I shewed those Gentlemen an experiment that surpriz'd, as well as convinc'd them. And that which more satisfi'd me my self, was a Tryal that I carefully made by a way which having men∣tion'd, but not yet (for want of opportunity) disclos'd to His Majesty, the Respect I owe Him forbids me to impart without His leave: On which account I hope you'll be content to be at present assur'd of these two Things; One, that by this way of Tryal, I found▪ (what possibly you will think strange;) that if there were in Water, so much as one Grain of Salt, in above two Ounces of Water, I could readily disco∣ver it: The other, that even by this critical Exa∣men, I could not detect so much as a thousandth par•• of Salt in Our Prepar'd Water; whereas I found by Tryals purposely and carefully made, that ou•• English Sea-water contain'd a 44, or 45th par•• of good dry Salt; or, which is all one, that 44 Pints or near so many Pounds of Marine Water, woul•• yield about one Pound of dry Common-Salt.

Thus Sir, you have a short and Art-less Account such as my haste will permit, and the nature of th•• Subject requires, of my part in promoting this pro¦fitable Invention; to which I own my self a grea•• well-wisher, not out of any private Interest (th•••• that was obligingly proffer'd me by the Patentees but as I think the bringing it into general us•• may prove a real Service to Mankind, upon th••

Score of divers Ʋtilities and Advantages, which yet, (tho I had leisure,) I should think very need∣less to enumerate to so discerning a Person as Dr. B. to whom I shall therefore hasten to subscribe my self,

SIR,

A very Affectionate Friend, and Humble Servant, R. BOYLE.