y incline,eitber by the vfuall incli-11 atorie quadrant, or by fitting a thread and plummet vntothe SeUor. For let the SeUor be opened to a right angle, the lines ofSines to an angle of p2^r. the inward edges of the SeRor to90 gr* and let a thread and plummet be hanged vpon a lineparallell to the… … right building) you may trie it by holding the Seftorfo thatthe thread may fall vpon^his plummet line. For then if theverticall edge of thcS*#*r mail lie clofe to the plane, theplane is erect, and therefore faid to be verticall 5 and ifyou draw a line by that edge of the Sfttor, rt mall be a…
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