Socius mercatoris: or The merchant's companion: in three parts. The first, being a plain and easie introduction to arithmetick, vulgur and decimal, the extraction of the square and cube roots, with a table of 200 square roots, and their use in the resolution of square equations. The second, a treatise of simple and compound interest and rebate, with two tables for the calculation of the value of leases or annuities, payable quarterly, the one for simple, the other compound interest, at 6 per cent. per annum, with rules for making the like for any other rate. The third, a new and exact way of measuring solids in the form of a prismoid and cylindroid, with the frustums of pyramids and of a cone: whereunto is added, some practical rules and examples for cask-gauging. By John Mayne, philo-accomptant.

To the Ingenious Author, concerning his DECIMALS.

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SIr, by your Art, and Pythagorean Pen, I'd prove a Metempsychosis agen; And were His Soul of Decimals but made,

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As Plato's Soul o'th' world of Seven is said, I'd swear 'twas slunk to you; but that you shew

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More Skill than e're his rambling fancy knew. Let roving Rabbies praise their Seven and Four;

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We'l shew them Mysteries enough and more: The Heav'nly Orbs are Ten, their Motions all

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Conspire to make a perfect Decimal: This is their Musick, and they shall be thus,

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In spight of Tycho or Copernicus. 'Tis said the Muses are but Nine, but who

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(Rather than fail) cann't add Apollo too? Thus may we range the world, and quickly find,

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We all to th' number of our Fingers bind. Thus Logick all the wandring Species brings,

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And places under tenfold Heads of things. Thus I, to give the Author praise in all,

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Reduce my Verses to a Decimal.

On his GAUGING.

YOur Circles, Sir, would make my folly ghess, You were a Conjurer, though you wo'n't confess. And Gauging is the rugged dev'lish Name Of some Hobgobling Imp, the very same That brought in Custome; but what e're he be, He's a rare Fellow at the Rule of Three: He doth just square the Circle; nay so true, That the King's Right is given to a Cue. There's none else such Impossibles can do: You give the King's, I give this Right to you.

I. W.

On his worthy Friend Mr. J. Mayne, the Author of this BOOK.

Ingenious Artist, whither do'st aspire? Or why t' outvye the Ancients do'st desire? Have they not left enough to following Ages? No: Thou their Master art, they but thy Pages.

My feeble Muse can never soar so high, As thy Deserts herein extend, nor nigh. Yet give me leave hereof to speak my mind: No Man could better teach us in this kind, Each Part so useful, and so plain I find.

T. W. 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉.

To his ingenious Friend the Author Mr. John Mayne.

WHo reads thy Book with an im∣partial Eye, Will see how plain, and how ingeniously Thy Rules are fram'd; here every Child may learn Arithmetick, which doth the Truth discern. The Iudges of our Realm could not dispence To all Men Iustice, were't not fetch'd from hence: Those Sons of Mars that furrow Neptune's Brow, Unto this Science must their Labours bow: The wealthy Merchant, and all Traders, hence Must calculate their Gain, or their Expence: The greedy Miser, here may plainly see His Pelf's increase at Compound Vsurie: The Purchaser of Farms, may also here, Value his Lordships, whether cheap or deer. Thy Squares and Cubes, methinks, so plain do seem, That I old Euclid should thy Father deem. All Humane Arts, Mechanical and Free, For this Companion are oblig'd to Thee. By Lines and Numbers, we our Buildings bring In due proportion, framing every thing. By these our Wooden Walls and Towers are fram'd, Which guard our Island, and the Seas command:

These fill our Stores with rich and costly things, Born from both Indies under Canvas Wings: These fortifie our Towns with Forts, by Line; By these we learn our Foes to undermine: By these th' Excise and Customs we do scan, Without Injustice to the Trading Man. Thanks to our Author then, that hath set forth These Arts so plain, and of abundant worth: Which do to Sea and Land such Profit yield, In Court, in City, Garrison, and Field.

Hugh Handy, Philomath.