In several different places I have discussed the existence and length of
what the mathematicians of the sixteenth century _used_, and those of
the seventeenth _talked about_, under the name of the _geometrical
foot_, of four palms and sixteen digits. (See the _Philosophical
Magazine_ from December 1841 to May 1842; the _Penny Cyclopædia_,
"Weights and Measures," pp. 197, 198; and _Arthmetical Books_, &c, pp.
5-9.) Various works give a figured length of this foot, whole, or in
halves, according as the page will permit; usually making it (before the
shrinking of the paper is allowed for) a very little less than 9-3/4
inches English. The works in which I have as yet found it are Reisch,
_Margarita Philosophica_, 1508; Stöffler's _Elucidatio Astrolabii_,
1524; Fernel's _Monolosphærium_, 1526; Köbel, _Astrolabii Declaratio_,
1552; Ramus, _Geometricæ_, 1621. Query. In what other works of the
sixteenth, or early in the seventeenth century is this foot of palms and
digits to be found, figured in length? What are their titles? What the
several lengths of the foot, half foot, or palm, within the twentieth of
an inch? Are the divisions into palms or digits given; and, if so, are
they accurate subdivisions? Of the six names above mentioned, the three
who are by far the best known are Stöffler, Fernel, and Ramus; and it so
happens that their subdivisions are _much_ more correct than those of
the other three, and their whole lengths more accordant.