17th century surveyor's crossI've obtained this instrument in 2009 together with the Wild TC1 total station in my collection, although the latter was a donation (by the same person who tipped me off this instrument) while this one was bought through a Dutch auction site. The instrument combines the functions of an equerre with those of a graphometer and pantometer and might have been used for setting out ground plans for fortresses (see below). A period name for this instrument is not known. I call it a surveyor's cross as the alidade can be fixated at 90 degrees using a screw and a threaded hole on the instrument, giving the instrument its most basic function (see below, at the rest of the possible angles it can not be fixated or clamped at all). Alternatively it could be called a graphometer as it has a scale running from 0 to 180 degrees, but apart from that type of scale graphometers typically were made with a much larger diameter half circular frame.
Dating the instrumentDating the instrument is another matter. An inquiry on the Rete newsgroup resulted in useful information. First reaction came off-list from a former keeper of the Binding Collection at the Koninklijke Bibliotheek in The Hague. He wrote that "...the box has a marked late Middle Age look: with blind tooling in a diaper pattern and roses within (see figure 2 and figure 7). But the roses are not of the Middle Age type - rather of the 17th century and possibly even 18th. The sturdy leather also has an old look. For the larger part of Europe, I would guess that one wouldn't use blind tooling on such a box after c. 1660. But if the box were German, it could also be later. [...] We know of blind tooled bindings (intended to look nice) from well into the 18th century. With my bookbinding knowledge (but with boxes it may be different), I wouldn't place this box after 1750, would not really be happy with the 18th century.".
Although this leaves a rather large gap of roughly a century, it can be narrowed down using the information I received on-list from David Coffeen of Tesseract. He wrote that, based on the style (compass, decorations on box and instrument, visor shapes, see figure 9 and figure 13) that it could be "...17th c., probably rather early..." and "...looking at the numeral shapes (note the 1,7) (see figure 4) and the wingnut shape (figure 5), [it was made] probably around the low countries -- Holland, Belgium, north Germany -- quite possibly Flemish...". On the instrument the word "Poligon" can be found (see figure 4) and it was suggested to me that this could indicate a Germanic origin,1 but as the compass has Latin annotated cardinal points (see figure 3) I later realised that it could be Latin as well.
The 30mm diameter central compass is of an old design (see figure 3). Not only the needle is set in a pyramid shaped brass block, but the cardinal points are all annotated in Latin; SE, OR, ME and OC (Septentrionalis [north], Orientalis [east], Meridionalis [south] and Occidentalis [west]), a type of compass used from at least the 16th up to the 18th century.2 The shape of the visors (see figure 13) - or rather the width/height ratio of them - indicate early 18th century or older as from the second half of that century they tend to be twice as long in ratio, while the pointer on top disappears.3
The previous owner told me it came from his father's estate and that it was as long in the family as he could remember. His father died recently well in his 90s and used to be a school teacher in Wernhout, Breda, Zevenbergen and Gemert and possibly received or bought it during that time from one of his student's parents or got it through his family. The first three places he worked in are all in the south-west of the Netherlands, the last in the south-east, and all are pretty close to Flanders. A part of his family (uncles and aunts) even lived in Belgium (Turnhout was mentioned). Taken the fact that in those days people could not travel as easily as we are used to nowadays, one would not expect a relatively simple instrument like this to travel large distances. This then might confirm its Flemish origin in which case it would have been from the second half of the 17th century at most. It still could be German (I may not rule that out) in which case it could be quite a bit younger. The lack of elaborate engraved decorations seems to indicate late 17th century as well, although undecorated earlier instruments are known to have survived.
The instrument came complete in its original elaborately decorated leather box (see figure 2 and figure 7) with green lining. Through time the hooks that were used to close the box have disappeared, while the lid had separated form the hinge (I managed to put them together without causing further damage). When inside the box the suspension ring of the instrument protrudes from it (see figure 2), so it seems that the instrument was carried by that ring during transport, perhaps suspended from a rope and hung around the neck or waist.
On the 55.5mm diameter limb two scales can be found (see figure 4); one divided in whole degrees, while the other - annotated with Poligon - represents the polygon scale. The latter can usually be found on a number of measuring instruments, from the surveying compass to the radio latino to proportional compasses.4 It serves to draw regular polygons, generally from the equilateral triangle to the dodecagon.4 With this particular instrument it would even be possible to create an icosagon (20 sided polygon).5 Being on a circular scale is quite unusual, although it also can be found on Hollandse Cirkels (Dutch Circles), and indicates that the instrument might have been made to set out the ground plans for fortresses as these were usually made of pentagons, hexagons etc.1,6
The alidade is 137mm in overall length (133mm between the points of the visors) can be locked in the 90 degrees position by turning a winged screw into a threaded eye on rim of the limb (see figure 5). It also has a pointer to read off the scale when used as a Graphometer or to set it at the desired angle at the polygon scale. The visors only have a slit to look through so lack the typical (horse-hair) threads found on later instruments like the Equerre and Graphometer in my collection. The ones on the main body of the instrument are 142.5mm apart, while the whole body (without the suspension eye, hinge and ring) measures approximately 161mm.
The figures on the scales and the Latin abbreviations at the cardinal points are all hand engraved (see figure 4). During that process the engraver made one mistake; instead of '15' he engraved '50' at the fifteenth line of the polygon scale (clearly visible at the far right on figure 4).
As the handle is hollow and tapered (18.3mm diameter at the opening and 51.5mm deep) the instrument could be fitted on a staff or tripod like most similar period instruments. In addition to that the instrument could also be used vertically - for measuring vertical angles while suspended from the ring (see figure 6) - although the handle is slightly too heavy, causing the instrument to tilt sidewards a few degrees.
: With thanks to Otto van Poelje for explaining the polygon scale and its possible Germanic origin to me.
: For a similar compass from the 16th century see: Epact, from the 18th century see: National Maritime Museum
: See H.C. Pouls, De landmeter Jan Pietersz. Dou en de Hollandse Cirkel, (Delft, 2004).
: Institute and Museum of the History of Science
: Name from proposed list of polygons at The World of Math Online
: Pouls, H.C., De landmeter Jan Pietersz. Dou en de Hollandse Cirkel, (Delft, 2004), p.55.
If you have any questions and/or remarks please let me know.
Equerre 19th century Pantometer? 20th century Pantometer Pantometre à Lunette 17th C. Surveyor's Cross Pseudo Holland Circle Graphometer