In my History of the Slide Rule I treat of Seth Partridge, Thomas Everard,
Henry Coggeshall, W. Hunt and Sir Isaac Newton.[32] Of Partridge’s Double
Scale of Proportion, London, I have examined a copy dated 1661, which is
the earliest date for this book that I have seen. As far as we know, 1661
is the earliest date of publications on the slide rule, since Oughtred and
Delamain. But it would not be surprising if the intervening 28 years were
found not so barren as they seem at present. The 1661 and 1662 impressions
of Partridge are identical, except for the date on the title-page. William
Leybourn, who printed Partridge’s book, speaks in high appreciation of it
in his own book.[33]
In 1661 was published also John Brown’s first book, Description and Use of
a Joynt-Rule, previously mentioned. In Chapter XVIII he describes the use
of “Mr. Whites rule” for the measuring of board and timber, round and
square. He calls this a “sliding rule.” The existence, in 1661, of a
“Whites rule” indicates activities in designing of which we know as yet
very little. In his book of 1761, previously quoted, Brown gives a drawing
of “White’s sliding rule” (p. 193); also a special contrivance of his own,
as indicated by him in these words:
A further improvement of the Triangular Quadrant, as I have made it
several times, with a sliding Cover on the in-side, when made hollow, to
carry Ink, Pens, and Compasses; then on the sliding Cover, and Edges, is
put the Line of Numbers, according to Mr. White’s first Contrivance for
manner of operation; but much augmented, and made easie, by John Brown.
He gives no drawing of his “triangular quadrant,” hence his account of it
is unsatisfactory. He explains the use of “gage-points.” His placing
logarithmic lines on the edges of instrument boxes was outdone in oddity
later by Everard who placed them on tobacco-boxes.[34] In Brown’s
publication of 1704 the White slide rule is given again, “being as neat and
ready a way as ever was used.” He tells also of a “glasier’s sliding rule.”
William Leybourn explains in 1673 how Wingate’s double and triple lines for
squaring and cubing, or square and cube root, can be used on slide
rules.[35]
Beginning early in the history of the slide rule, when Oughtred designed
his “gauging rod,” we notice the designing of rules intended for very
special purposes. Another such contrivance, which enjoyed long popularity,
was the Timber Measure by a Line, by Hen. Coggeshall, Gent., London, 1677,
a booklet of 35 pages. Coggeshall says in his preface:
For what can be more ready and easie, then having set twelve to the
length, to see the Content exactly against the Girt or Side of the
Square. Whereas on Mr. Partridge’s Scale the Content is the Sixth Number,
which is far more troublesome then [even] with Compasses.
One line on Coggeshall’s rule begins with 4 and extends to 40, these
numbers being the “Girt” (a quarter of the circumference), which in
ordinary practice of measuring round timber lies between 4 inches and 40
inches. This “Girt line” slides “against the line of Numbers in two
Lengths, to which it is exactly equal.” A second edition, 1682, shows some
changes in the rule, as well as an enlargement and change of title of the
book itself: A Treatise of Measures, by a Two-foot Rule, by H. C. Gent,
London, 1682. In this, the description of the rule is given thus:
There are four Lines on each flat of this Rule; two next the outward
edges, which are Lines of Measure; and two next the inward edges, which
are Lines of Proportion. On one flat, next the inward edges, is the
Square-line [Girt-line in round timber measurement] with the Line of
Numbers his fellow. Next the outward, a Line of Inches divided into
Halfs, Quarters, and Half-Quarters; from 1 to 12 on one Rule; and from 12
to 24 on the other. On the other flat, next the inward edges, is the
double Scale of Numbers [for solving proportions]. Next the outward on
one Rule a Line of Inches divided each into ten parts; and this for
gauging, etc. On the other a foot divided into 100 parts.