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A water Level fhewS the horizontal line, by means 

 of a lurface of water, or other liquid, founded on 



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this principle. That water always naturally pi 



felf level. 



The moft fimple inftrument for this ufe is made 

 of a long wooden trough, or canal, whofe fides are 

 parallel to its bafe, fo that, being equally filled with 

 •water, the furface thereof fhews the line of Level. 

 This Level is alfo made with tv/o cups fixed to the 

 two ends of a pipe three or four feet long, about an 

 inch in diameter-, by means v/hereof, the water com- 

 municates from the one to the other cup, and this 

 pipe being moveable on its ftand, by means of a 

 ball and focket, when the two cups become equally 

 full of water, the two furfaces mark the line of Level. 

 Inftead of cups, this inftrument may be made with 

 two fliort cylinders of glafs three or four inches long, 

 fattened to each end of the pipe with wax or maftich ; 

 then the pipe, being filled either with common or co- 

 loured water, will fliew itfelf through the cylinder, by 



. means of which the line of Level is deterniined, the 

 height of the water, with refpedt to the center 'of 



■ the earth, being always the fame in both cylinders. 



: This Level is very commodious in levelling fmall 



diftances. ' -*■:,:::; rTcVv^"^?^ 



: If you would level any jJiece of ground that'ybii tan 



. fee from fide to fide, or from the middle to any fide, 



; fet up your inftrument iq the middle of it; whether it 



1 be a water Level^ or _a ground Level with fights ; 



.' place it fo high, that you may fee over the higKeft part 



, of the gi-oiind half a fooF or a foot ; then fet up a 



ftakc in the middle^ fo that tRe topi may be fexaftly 



level with.t;he fights, and another ftake on the higheft 



fide, the top of which muft be level with the middle 



. Y ftake; then cither turn the Level, or look-back fight, 



^Y and fet up another ftake on the lower ground level 



I with the two firft ; then you will have three ftakes 



U; ftinding in a Level. 



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and mo polcn from the top of that hill, thofe fjiir 

 feet are to come out. . . 



To pcrform^ this, ft-t up a ftakc on the top of a !*ill 

 two or three feet above. ground, and another of tiie 

 . fame height where the depth come; our, Jcc duv/n a 

 ftake three rods from that, till the head corner co Le 

 in a line with thefe two, and at that ftake you muft be 

 one foot deep. • . . 



■ At fix poles ftake down another as before, and there 

 you muft be two feet deep : then ftake down anoiHcr 

 at nine poles, and there you muft be three feet 

 deep, and you may fet more ftakes at equal dif- 

 tances, which will direct you fo as thac you cannot 

 go amifs. 



LEVITY is the privation or want of weight in any 

 body, when compared with another which is heavier, 

 in which fenfe it is oppofed to gravity. . . i" 



The fchoolmen maintain, that there is fuch a thing as 

 pofitive and abfolute Levity, and impute this to the 

 rife and emergency of bodies lighter in fpecie than ' 

 the fluids wherein they rife. : / - . ..ir 



But, befides that the commoh fenfe of manlcind dif- 



- covers, that Levity is only a relative term, we find 

 -that all bodies tend towards the earth, feme flov/cr, 

 ;. and fome fafter, in afl fluids or mediums, whether 

 i>r water, air, 8z:c. =" .; M^' . .. . . •' 



-;: Thus cork is faid to be lighter than gold, becaufe ' 

 V. under equal dimcnfions of bulk the gold will finjc in, 



and the cork fwim upon the water. 



Archimedes has demonftrated. That a folid body 



- will float any where in a fluid of the fame fpecitic 

 . gravity, and that a lighter' body will keep above a 



■ heavier." i ::• -' 



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Then keeping your Level true to tne middle ftake, 



r turn it till it makes right angles with the' three ftakes, 



• The reafon of this is, becaufe bodies falling towards, 

 the earth, thofe whith have a like number of ec^ual 

 parts, have equal gravity,' fince the "gravity of the 

 whole is the fum of the gravity of all its partsi' T^cX 



Now, tv/o bodies having an equal number of equal 

 parts, if under the fame dimeniions there are no inter- 

 vals defti'tute of matter j whence It follows, that as no 



I,, and fet up two ftakes on each fide 5fte Level' with I portion of matter is fo fmall, but that body whercia 



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thdfc three, then you will have five fbkes in two lines 

 let true level; 





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If the gi^ound be lar^e, you may fet up two rows 

 rnore by the Level, but five ftakes are ertougli fn a 

 fmall groundi:*^ 



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it is contained may be wholly divided mto parts 

 equally fmall, there can be no reafon for the delcenc 

 of thefe, which will not hold equally forthe defcenC 

 of that. 





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•:,"When this is done, you may lay yourl,eyel afide, 



- and look over the head of one to the head p? Another j 

 " and caufe the periori wKb affifts you to put down 

 r! ItaKes between t\^o iand two, till you have fet as ^lariy 



ftakes level in the gr(5uild afe ybu thirik cbnvenlerit \ or 

 ■Joyou may ufc a rUk, which being placed leydwith 

 :n the head of the ftake^ you mav look over that to the 

 ; head of the other, and put flakes doWn between you 

 Jt**aria the other ftake,- to what number yoii pleafe. -; 



The ground bein^ thus ftaked 6ut with all the ftakes 



.ft: heads level, and half. a. foot higher thgn the higheft 



r^P&ttnd, in fome grounds tte middle ftake^ and the 



ftakes in the croS lint, will be the Level line^the 



L ground muft be brought to ; tlmt is, abating tKe hill, 



t.and filling lip" the low fide to the Level of the mid- 



-i Hence it "maybe concluded, that thofe bodies which 

 do not equally gravitate under the fame dimenfions^ 

 -J do not contain the fame equal portions of matter, and 

 -yi therefore whtn we^ec, that a cube of gold fubfides in 

 - water, at the fame time that an equal bulk or cork 

 ;n fwims' upon it, it is evident, that the gold muft have 



ii'z greater number of. equal parts of matter under_ the 

 ^^Jame bulk than the cork, or the corjc muft have z 

 *.- greater number of vacuities than tlie gold, and that 

 \ there are alfo in the water a greater number of Vacui- 



.. tic^ than In the ^old. . 



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roportion 'ydur ground to that. : 

 -^* As for inftance : If -> valley be ten poles in len^ 



: and two feet in depth from the ftrait line, \n^ there 

 ? Jbe ahill five poles long ; how itiiHy feet dedp muft a 

 ^ perfon fiiik thofe five p6les ft fill up the valley? 



This queftion msy ttt rtfolved by the iiivferife x)r fa^ck 



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HenCe we have a clear idea both pf degfity or gravity,' 

 and of Levity, and know, that in a ftrict fenfe the 

 latter cannot be accounted any thing pofitive, buf a 

 mere negation, bi- abfenccof body,"which determines 



that body to be'lighter than d^nother which contains 

 line. But if the ground be very uneven, then yout rrmoit i^attef,^ m^^&^^v^ r-^ir j i:?-H v.-^,;-^^. -7.. 

 muft meafiif^ Bter all the ftakes, and takt them mid- LI C ri E N. Livefsvorti , . . ^ - 



die high for their mean of Level, and, by the rule |t: There being two forts of this plant which are ure4 

 t^Of three, proportion 'Vdur ground to that. : - r^^^^ in medicine, and one of thofe being accounted a fo* 



fi^vereign remedy for the Bite'of mad dogs, I thoiight it 

 Cwould not be improper to mention them here, though 

 ' they are plants which^ cannot be pjopagated by any 

 :;/ method, except by paring up jhe , turf ^f Graft 

 i^n^hfereon they growy and laying it down on fome moiit- 

 ihady place, where, if the turf takes root, and 





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.: rule of three;- an^. will ftand thus; As 5 W 2, fois I :,fhady place, where, if the turf takes rooi 

 ^* lOtojLH i<:Ji.^...^z! c:-:S^li>: *^:^^i-^#:5^^.*;'*l " tI t ''tfirives, the plants will Ipread and'dd well, 



-k- ?-z::.:r^ .:-Z:f^^ ->in:;t^ta,l> ^leiil.rrhe two Sorts art, ^. :fdj_>t^*:=..,:: v .. . 



^■i^V.-^J v*^;fcs^^;/:?-. ^'/4> rn^ : -/.i;.-^^ofr* J| J';-IiicHEN~ f P^/r^xwT "petraeus latifolius, hve 



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latifolius, five Hepa* 



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Syn. 



{Petrous) "petraeus 

 -f tica foritaila. C. B. P. Common Ircad-kaved Lherwort. 

 2.' Lichen (Q^wr«»») terreflris cinereus. Raii 

 . ' I Jl/h-coloured Ground Liverwort. ■ - 



S' So that a perlon muft go lour ftet deeiJ In fuch'a hill I -The'lirft fort growro'n the fides of wells, and jn moift 



- -- • _ ' • - ' '• '■ " - ^ '• •'" "-' ' ' feadf plaCrt, not only on the ground, but on fton-s, 



you arc to abut the top of the hill fourifc^^p, I -'^ttifikf, or wood. Of this there^are feveral varicne-?. 



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