When this Book was first committed to the Press , I sent an intimation thereof to some of my friends , for their encouragment to it , a Practice now common , and commendable , which hath not wanted a considerable success , as witness the respect of many worthy persons , to whom I am oblidged . But there is a Generation , that rather , than they will encourage any new Invention , set themselves by all means to detract from it , and the Authors of it : so grieved are they , that ought of this kind should fall into the hands of any , but their own . And therefore , if the Author shall give but the title of New to his Invention , though never so deservedly , they fly presently in his throat , like so many Wild-Catts , studying either to Ridicule his work altogether a trade that usually , the person of weakest abilities , and most empty heads , are better at , than learned men , like those Schollars , who being nimble in putting tricks , and impostures upon their Condisciples , were dolts , as to their Lesson , or else fall upon it with such snarling , and carping , as discover , neither ingenuity , nor ingeniousness , but a sore sickness , called Envy .

In the Intimation , I affirmed , that the Doctrine concerning the Weight , and Pressure of the Water was New . This one word , like a spark of Fire falling accidentally among Powder , hath been the occasion of so much debate . Their ground is , because they look upon the Hydrostaticks , as a Science long ago perfected , seing Archimedes 2000 years ago hath demonstrat the Water to have a Pressure , and some others since , as Stevinus . They affirm likewise , that all the Theorems , and Experiments , that are here , are either deduceable from Archimedes , and Stevinus , or are the same with theirs . If these Gentlemen had suspended their judgment , till this Book had been published , I suspect they would not have spoken so confidently . For Archimedes his proposition ; they are but few , and proven ( as Mr Boyl saith ) by no very easie demonstrations , which have more of Geometrical subtility , than usefulness in them . But these , which are here proposed , are not only useful , but evidently evicted by reason , and sensible Experiments , even to the meanest capacities . And though some of mine , may ( perhaps ) co-incide with some of his , which to me is but accidental , yet our way of procedour is toto Coelo different . His way is more Speculative : this is more Practical . His demonstrations are Geometrical : these are Physical . His propositions are but for the use of a few : these are for the use of all . His are not illustrated , and confirmed by Hydrostatical Experiments : these are .

Stevinus a late Writer keeps that same method . Yet I judge it easie to let see , even in the entry , how little cogent some of his demonstrations are , without derogating from such a Learned Man . He hath indeed some Pragmatical Examples ( as he calls them ) for illustrating some of his Geometrical Propositions , anent the Pressure of the Water ; but I leave them to be considered by the judicious and understanding . Again , in this Method , I am yet as much different from others , who have written lately , as from these I have been speaking of . For , I not only treat of the Pressure of the Water , but takes in with it , the Pressure of the Air joyntly ; since to explicat sufficiently the Phenomena of the Hydrostaticks , without it , it is impossible . And yet fu●der , I not only counterpoise Air with Water , but Air with Mercury and Water with Mercury , by which means several mysteries , and secrets in this Art , are discovered .

There are several Inventions found out of late in the Hydrostaticks , whose events and effects , cannot be clearly deduced from the grounds of Archimedes , and Stevinus , who had not that clear discovery ( fo● 〈◊〉 we know ) of the Pressure of the Air , that some now have , without which , these effects can never be sufficiently explained . And who doubts , but others afterwards , may make farder discoveries , and profit the world yet more , with their Inventions , then any have yet done . Is then the Hydrostaticks , a Science long ago perfected ? To this Pedantick Conceit , I must again oppose the judgment of Mr. Boyl , who saith moreover , that the usefulness of this part of Philosophy hath been scarce known any farder than by name , even to the generality of learned men .

But let us suppose , that the notion of the Pressure of the Water , is of an old date , even as old as the Flood ( for Noah surely knew , that the Pressure of the Water , would sustain the Ark ) and ( giving , but not granting ) that Archimedes 2000 years ago hath written all the Principles of the Hydrostaticks , doth this hinder any man now , from deducing new Conclusions from these old Principles ? But there is here , no such thing ▪ for neither in this , nor in my last Piece , are my Adversaries able to trace me . 'T is like the purposes would have been so much the better , if I had followed other mens foot steps : and it is like they might have been so much the worse . I doubt not , but I have lighted upon other mens thoughts in some things : and others writting on this same subject , who perhaps are my Antipodes , may fall upon mine . My Antagonists affirm , they are able to deduce all my Theorems , and the events of all my Experiments from the grounds of Archimedes and Stevinus . If they take not their word again , I hope they will do it ; for now I put them to it . And though they should , ( which I am not affraid they shall do in haste ) yet they must prove next , that these Theorems and Conclusions , so deduced , are not new , which all their Logick will not prove . But what if we do more , ( say they ) even overthrow many of all your Aerostatical and Hydrostatical Experiments , in this , and in your last Peice ? I give you liberty , and for your hire , a Guiny for each Theorem , or Experiment , you are able to ransack , in either of the two Books , though they come near to an hundred . But , ye must oblige your selves ( my Masters ) to do it with Reason , laying aside your Sophistry and Canina eloquentia . And this I offer , Reader , that I may reduce them , to a better humour , and encourage them to leave off flyting , and only use reason . Neither must they be like the Wasp , that only lights upon the sore place . But if they love to kindle any more fire , they will find me proof against it . If it burn them , it shall not heat me . Nevertheless , if they love to juik under deck , like Green-horns , having no courage in themselves , or confidence in their cause , they must excuse me , if at last , I write their names upon a Ticket , and bring them above deck . This is all I have to say , at present ( Reader ) and I bid thee farewell .