A LETTER of Mr. BOYLES, to the Learn­ed Doctor JOHN BEALE Fellow of the Royal Society, concerning Fresh Water made out of Sea-Water, printed at the Deſire of the Pa­tentees.

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 publik Gazzet; I muſt inform you, that one of my neareſt Relations, (Captain Fitz-Gerald) and ſome other worthy Gentlemen, having acquainted His Majeſty, that they had an Invention for making Sea-Water ſweet and wholeſom 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 Expreſſions, to command me to attend Him, with a further and more particular Information. Having readily obey'd this Order, and been made acquainted with the Objections the King thought fit to make againſt the Practicableneſs of the Invention; which, (though a private man had urg'd them,) I I ſhould think the moſt judicious that have been fram'd againſt it, I humbly repreſented to Him, that I look'd upon this Inven­tion as compriſing two differing things; a Mechanical part, which related to the Engine it ſelf and the uſe of it a Ship-board,12 and a Phyſical part which concerns the Potableneſs and Whole­ſomneſs of the Liquor. About the former of theſe I did not in­tend to clear the Difficulties, eſpecially ſuch ſtrong ones, as His Majeſty had propos'd; but left it to the Patentees to give Him Satisfaction, which they were in a readineſs to offer. But as to the Wholeſomneſs of the prepared Water, I had made ſome Trials upon that Liquor, which gave me no juſt grounds of ſuſpecting it to be unwholeſome, but ſeveral Motives to believe it well condi­tioned, and of great uſe to Navigators, and not to them only. And having hereupon briefly acquainted His Majeſty with the chief Trials I had made to examine this Sweetned Water, He was pleaſed to look upon them as ſatisfactory, and vouchſaf'd on that occaſion to diſcourſe as a Virtuoſo of the Sea and Brackiſh Waters, and gave me ſome new, as well as 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 Ʋtilitie the Publick may receive by a cheap and eaſie way of preparing it:) Firſt, then I conſidered that almoſt all the Rain water that falls from the Clouds on the Main Ocean, and which (except perhaps in very few places in Torrid Climates) is unqueſtionably receiv'd as wholſome, muſt be afforded by the Sea, and conſequently be but Seawater freed from its Salt (according to the Famous Motto, Redit Agmine dulci.) Next I found, as His Majeſty Himſelf had done,) that the Liquor was well taſted, and without any ſenſible Brackiſhneſs; and ſo ſome of it continued for between 4 or 5 Months in a large Chryſtal 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 ſmelled by ſeveral Learned Phyſicians of the Famous Colledge of London. Thirdly, I found it laver very well, which13 moſt Pump waters, and many others that have ſome little (though unperceived) common Salt in them, will not do. Fourthly, this Water will boile Peaſe tender, which amongſt Seamen 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 Liquors, I found this Water far leſs heavy than one would expect, for if it differed at all in weight from the like quantitie of undiſtilled Water, (I ſpeak with an If, becauſe it is far more difficult to be Exact in ſuch nice Trials, than the Ʋn­practiced will Imagine) the difference was not conſiderable being but 1 part in 400; and that difference is very ſmall in Compa­riſon of that which Navigators and Learned Authors relate to be obſervable in Natural Waters, all of them good and potable: I might tell you on this occaſion; that the laſt Great Duke of Tuſcany, who was an Eminent Virtuoſo, and the Patron of the Celebrated Academy of the Lyncean Philoſophers is affirmed among other prudent courſes that he took for his Health, where­of he was very Solicitous to have conſtantly made uſe of Diſtill'd Water for his own Drinking. And I could add other things fa­vourable enough to the Patentees Water, if Haſte, and perhaps Diſcretion too, did not oblige me to leave them yet unmention'd, that I might now have time to ſay ſomewhat of the main thing of all that convinced me of the Saltneſs of the Water I ſpeak of. I conſider'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 Encourage the Makers of ſuch Attempts, was to Free the Sea­water from the Brackiſhneſs without any Noxious Additament: ſo that on all ſides it was taken for granted, that the only thing that kept the Sea water 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 long14 ſince written a ſhort Diſcourſe of the Saltneſs of the Sea; I had been induſtrious to deviſe ways of comparing Waters in point of Brackiſhneſs. And by theſe I found the Patentees Water to be more free from common Salt, than Waters that are uſually drunk here in London, of which I remember I ſhew'd thoſe Gentlemen an Experiment that ſurpriz'd as well as convinc'd them. And that which more ſatisfied me my ſelf, was a Trial that I carefully made by a way which having mention'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'l be content to be at preſent aſſur'd of theſe two things; One, that by this way of Trial, 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 diſcover it: The other, that even by this critical Examen, I could not detect ſo much as a thouſandth part of Salt in our prepar'd Water; whereas I found by Trials purpoſely and care­fully made, that our Engliſh Sea-water contain'd a 44th or 45th part of good dry Salt; or, which is all one, that 44 Pints, or near ſo many Pounds of Marine Water, would 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 the Subject requires, of my part in promoting this profitable Invention; to which I own my ſelf a great well-wiſher, not out of any private Intereſt (though that was obligingly proffer'd me by the Patentees,) but as I think the bringing into general uſe may prove a real Service to Man­kind, upon the ſcore of divers Ʋtilities and Advantages, which yet (though I had leiſure,) I ſhould think very needleſs to enu­merate to ſo diſcerning a perſon as Dr. B. to whom I ſhall there­fore haſten to ſubſcribe my ſelf, &c.