Pantometer (Vernier Surveyor's Cross with Compass)

Physical description: A nickeled brass surveyor's cross in a wooden fitted case. The cross consists of a cylinder with a compass on the top and a gimbaled socket on the bottom for mounting on a stake or tripod. 

The main body of the instrument consists of a cylinder of two parts, the upper of which has two pairs of slits set at 90˚ to one another. The lower section has one pair of slits directly opposite each other (i.e., 180˚ apart). Each pair has two types of slits, the "eyepiece slit" which is a beveled slot with two beveled circular pinholes at either end (and thus looks like an elongated barbell), and the "objective slit", which is wider with a fine sighting wire strung vertically through it.  Both slits are 30mm tall with the eyepiece slit <1mm side, and the objective slit about 4mm wide strung with <1mm diam. wire.

There is a meridional band engraved where the top and bottom cylinders meet. The top edge of the lower cylinder is marked in 360˚ by single degrees and the lower edge of the upper cylinder has a Vernier scale marked 0–60' by 2' whose zero sligns with one eyepiece slit above. The second perpendicular set of slits sights 90˚ to the right from this principle set of slits.

On the bottom of the cylinder are two 20mm diam. knurled knobs.  One is geared within to allow the upper section of the cylinder to be rotated minutely and the other locks the rotation.

Functional description: The surveyor's cross is used to set a perpendicular to a given line during surveying, although this more advanced pantometer can sight a second line at a prceise angle to the baseline. One uses either the upper or lower eyehole depending on whether the bearing of the line descends or ascends from the current station, since the opposed slits can only be used in one direction each. Having set the top cylinder to zero on the 360˚ meridonal scale, the surveyor may either sight a given line of an existing survey and read off its compass bearing (this instrument therefore acting like a simple surveying compass) or set the instrument from a written survey description that includes a compass bearing. In this case one can use the lower sight to set a line, rotate the top cylinder a set amount, and then sight a second line and its perpendicular. Alternatley, by zeroing the cyllinders and sighting on one line with the bottom slits, the top cylinder can be rotated to another line and the angle between read off the meridonal band to 2' of arc.

The typical method of use for a simple cross would be for the surveyor to take a tripod out to a known survey point and then set the bearing of one of the slits (choosing the one pair so that the other pair sight either left or right as will be needed). Then by locking the head in place and sighting though the other slit, the surveyor's assistant ('rodman') can move as far away as desired and then adjust laterally until he is on the perfectly perpendicular line.

Further information: Gillespie 1901, 59-60; Schmidt 2007.

This particular form of a surveyor's cross was named a "Goniasmomètre" (Fr.) or "goniometer" (Engl.; literally meaning simply "an angle-measurer"), and seems to have been primarily favored in France (Gillespie, 1901, 200, no. 304). It is properly known as a "pantometer", an instrument for measuring all angles, and as a "Equerre d'arpenteur" (lit., a "surveyor's bracket"). In its most general form of a cylinder with slits, it goes back to the seventeenth century, but its dual-cylinder Vernier form seems to have been developed for military surveying about the first third of the nineteenth century, perhaps by a Mssr. Fouquier, of the École Polytechnique (Laisné 1839, 61). 

According to the label inside the storage case, this instrument was awarded a gold medal at the Brussels’ 1888 "Grand Concours: international des sciences et de l'industrie," part of the World's Fair there in that year. This relatively small expo is quite understudied, having been eclipsed the very next year by the Exposition Universelle in Paris (for which the Eiffel Tower was built). The pantometer was also awarded a “Diplome d’Honneur’ at the Exposition Internationale d'Anvers in Antwerp in 1894. The unknown maker apparently exhibited at 7 major European fairs (but no American ones) between 1851 and 1894, suggesting that this is likely a major and known maker.

The label and ink stamp in the case from two major expositions suggests that it was the type of instrument (or even just surveying instruments by this maker) that received the award, not this specific object.  In many cases the actual prize-winning object would have its medal mounted in or on the case as well.  The fact that the paper label has a pasted in label from an 1888 exposition and then a inked stamp from 1894 suggests that this particular instrument was made sometime between the two. Further research in the exhibitor catalogs for these exhibitions would be fruitful. [1]

It is interesting that there is no indication of the maker anywhere on the cross, or even on the labels, but this seems to be a not-uncommon feature of the type of instrument: see similar  and contemporaneous examples at the Harvard collection here and here (without a compass), and here from the Smithsonian; and a comparable early twentieth-century one here. There are similar pantometers known by instrument makers Salmoiraghi of Milan, H. Bretschneider of Halle, Stanely in London, and even after WWI by SLOM in Paris.

By comparison, a simple surveyor's cross (presumably without a Vernier) could be had from Gurley (1889, 304) for only $3 or $6 with a compass on top. They also sold a complex version "with vertical axis and divided circle, to take angles" for $12.

This example was purchased in 1984 at the monthly antiques market in Brussels by Bob Carnanan (MTU Class of 1953). Received by MTU Social Sciences and IHSI, July 31, 2019.

Notes
[1] A preliminary check of the 1894 Antwerp foreign exhibitors in  Class 8, "Objets scientifiques, cartographie, etc." (EUd'A 1894, 276-278) suggestst that this will be harder to figure out than not.  Of the 42 exhibitors from France, only two Parisienne firms are listed as potentially showing surveying instrumetns (Alfred Berthélemy showing "Instruments de précision, optiqiue, mathémathique, géodésie, nivellement, [et] topographie" and Vion Bros. of Paris, exhibiting "Instruments d'géodésie"), but numerous others are listed showing generic "precision instruments" or "instruments for the sciences." Specific items shown are not listed.

Nicolàs de Hilster, "Geodetic Instruments: Surveyor's crosses: Pantometer," n.d. [online].

Exposition Universelle d'Anvers [EUd'A], Catalogue officiel général. II, Sections étrangères (Bruxelles: A. Mertens, 1894).

William Mitchell Gillespie, A Treatise on Surveying: Comprising the Theory and the Practice (New York: D. Appleton, 1901).

Joseph Laisné, Aide-mémoire portatif à l'usage des officiers du génie (Burssels: Meline, Cans et Compagnie, 1839).

Wilhelm A. Schmidt, "Second Thoughts: The Surveyor's Cross," Professional Surveyor Magazine 27, no. 3 (March 2007)  [online]