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Show A Difcourfe of Foreft-Trees. Chap. XXX, s fetit foasit may beit dry; then cleanfe the Boal of the branche Chap.XXX. A Difcourfe of Foreft-Trees, , to which which were left, and fam it into lengths for the Jquaring ) which I callit orkmen belongs the Aéeafure, and Girth (as our H refer to the Buyer , and to many fublidiary Books lately Printed, wherein it is taught by a very familiar Calcwle Mechanical and ealie ? ethod. ie But by none in’ my apprehenfion fet forth , ina more facile and accurate way than what that Induftrious Mathematician Mr. Leybourn has Publith'd , in his late Line of Proportion mace Eafie, and other his Labours 5 where he treats as well of the Square asthe Round, as’tisapplicable to Boards and Superficials, and to Timber which is hew'd or lefle rough, in fo Eafe a Method, as nothing canbe more defired. 1 know our ordinary Carpenters, @c. have generally upon their Rulers a Line , whichthey ufually call Guaters-Line; but they few of them, underftand howto Work from it : And divers Conmtrey Gentlemen , Stewards, and Wood-men,, when they are to Azeafure Rough Timber upon the Ground , confide much to the Girt, which they do witha fering at about four, or five foot diftance from the Root or Great Extream : Of the Strings length, they take a quarterfor the true Square , whichis fo manifeftly erroneous, that thereby they make every tree fo meafur'd, more than a fit part Icfle than really it is. ‘This mifiake would therefore be reformed5 andit were Ci conceive) worth the Seller's while to infpect it accordingly : Their Argument isyThat when the Bark of a Tree is ftrippd, and the Body hew’d to a Square , it will then hold out no more meafure ; that which is cut off being onelyfit for Frel, and the Expenfe of Squaring cofts more than the Chips are worth. But let us however Convince themof this Error by confronting Mr, Leybourns Tables, PROB sd. A Tree being 68 Inches about, to find how much thereof in Length will make one foot /quare. SOL. A fourth part of 60 Inches, is 15, which they take for the due Square 5 wherefore look for 15 Inches ( viz. one foot three Inches ) inthe firft Column of the firft Table, and oppofite to It in the fecond Column, you fhall find 7 Izches, 6 tenth parts of an Inch (which is fomewhat above half an Inch ) will make one foot square. § 0 L. The fourth part of 136 is 34 inches in the firlt Colusn of the {e- cond Table, and 9 foot in the head ofit; and oppofite to the 34 inches, and under 9 foot.you hall find 72, 25. (viz. 72 foot 4) for fo much you may fellit, and no more , which is yet lefs than and the true content byabove a fifth part But fuppofing (as they ought to do) there were no fuch Wffe as is pretended 5 yeuwill find bythe third Table, how much in lengthof any Cylendrical Timber, whole Girt is known , will make a footfolid , and confequently , detect the Error of the former cuftoma ry practife. PERIOWB. THE A Tree being 60 Inches circumference, to know howmuchtheres of will make a cubical foot, SHOUL: Find 60 inches inthe firft Column 5 and oppofite toit in the {e- cord Column, you hall find o- 6-0 whichis to fay, 6 inches one- ly: The Confedarie is, that 6 iwchesin length of a Tree 60 inches circumference, will make a foot folid: Whereas by the other ufual procedure, you found there muft be 7 inches and above half an inch, to make fomuchs whichis above an ixch and half too much in everyfoots length, and what that amounts to in many feet ’tis eafy to imagine, So fuppofe a Tree be but 29 inches in circumference, the fame Table willin like manner thew, that it requires but 1 foot 2 inches and 3 tenth parts of aninchin length,to make ita foot folid of Timber ; and thus of any number as faras you will inlarge your Table, But then imagine that the fides of the fquareat the extremities of {quar'd Timber are unequal, as frequentlyit happens,byfometimes 5, 6, 16, or more inches difference: Some Artificers think they encounter this well enough by adding the two fides together, and taking thé woitie of the fide for the trxe {quare: But this is as erro- weows as the others efpecially, if the fides differ confiderably, Let one fide be 30 inches, and the other 138,thefe added ,make 213, the halt whereof is 1063, which theyeftimate for the true {quare; whereas in truth , the right {quare is 74 inches , and one tenth part; which demonftrates the error to be 32 inches and 4 tenths. Again, PROB. reformetherefore this egregious miftake, the fourth Table GIA € calculated to what number of inches you defire : Example. A Tree being 136 Inches about, and 9 Foot in length, to-kno™ how many/olid Feet the Tree contains ? sol, |
