142 The Description of

outer Hals there must be fixt a thinBrass Scale of an equal Length andBreadth with theBoxRuler,theBreadthof which Scale is to be divided, by Linesdrawn from End to End, into three e-qual Parts, and the Length into Inches,halflnches, and i oth. of an Inch,- theInches are to be drawn directly cross thewhole Breadth, andmark’d i. r. 3. 4.

both Ways to B and D ; the halfInches are to be drawn cross the middleand innermost Third, and the ioths.only cross the inner Third. Let therebe on one End of this Scale an Inch, andon the other End half an Inch, eachdivided very exactly into ten equalParts Diagonal Ways, that the Tenthsand Centefms which may happen in theOperations, on the Square and Indiceshereafter to be defcrib’d, may be exact-ly mealur’d on them by a Pair of Com-passes. The Reason for railing theouter Half of the Box Ruler, above theinner Half, two Tenths of an Inch, as

before