Commensurable Surfaces and Medial Lines
If ab is communicant with bc, the two surfaces are commensurable, proved by Euclid
This folio develops the Euclidean theory of commensurable magnitudes: "if line ab is communicant with bc, it follows that the two surfaces are commensurable," proved "using the tenth of the tenth" and "by the eighth." Segments are marked "root of 3," "root of the root of 108" and 6, and a long rectangle carries base 6, height "root of 3" and interior "root of 108." A rectangle divided lengthwise is lettered g, f, d, e, c and labelled "medial line," with further small rectangles marked a and b and a segment d c set off by a looping pen-stroke. The leaf is numbered 26.
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Commensurable surfaces from communicant lines
A rectangle divided lengthwise is lettered g, f, d, e, c and marked "medial line." The reasoning states that if line ab is communicant with bc, the two surfaces are commensurable, proved "using the tenth of the tenth" and "by the eighth."
Segments as roots: root of 3, fourth root of 108, and 6
Three line segments are labelled "root of 3," "root of the root of 108" and 6, giving the irrational and whole magnitudes handled on the sheet.
Rectangle 6 by root of 3 with area root of 108
A long rectangle has base 6, height "root of 3" and its interior labelled "root of 108," linking the rooted sides to the area they enclose.
Small rectangles a and b with segment d c
Set off by a curved pen-stroke, a rectangle is marked a and annotated "root of the root of 108," a neighbouring rectangle is marked b, and a segment below is lettered d c.