Putney, July 17.
THE GEOMETRICAL FOOT.
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.
A. DE. MORGAN.
Minor Queries
Plurima Gemma.—Who is the author of the couplet which seems to be a version of Gray's
"Full many a gem of purest ray serene," &c.?
"Plurima gemma latet cæca tellure sepulta,