These AMS radiocarbon analyses dated the materials used to manufacture the spheres. Although the resulting time ranges may seem large, the exercise made it possible to state with a good degree of certainty that the UNIL globes were produced in Mercator’s workshop in the 16th century.

Terrestrial sphereCelestial globe

Ill. Rapport LRD

Two samples were drawn from the terrestrial sphere near the South Pole, one from the surface paper and the other from the substratum fibres. The substratum is composed of a textile substance but it is difficult to be more precise.

The C/N (carbon/nitrogen) ratio of an organic material indicates to what extent it has changed over time and thus the speed at which it can decompose in the ground: the higher the ratio, the slower the decomposition process. In the case of the terrestrial sphere, the paper sample had a C/N ratio of 63.32 and the textile sample a C/N ratio of 23.73. This suggests that the paper was made from a textile substance, as was common in medieval times.

C14 radiocarbon dating yielded the following results :
Sphere, paper (surface)	1450-1640	probability 95,4%
Sphere, fibres (substratum)	1480-1650	probability 95,4%

Ill. 13, Rapport SIK|ISEA

Two samples were taken from the celestial globe, one from the surface paper and the other from the substratum fibres.

C14 radiocarbon dating yielded the following results :
Sphere, paper (surface)	1458-1706	probability 58,0%
Sphère, fibres (substrat)	1473-1640	probability 95,4%

C₁₂ and C₁₃ analyses of the spheres

Besides the conclusive C₁₄ dating of the stands, additional C₁₂ and C₁₃ tests were conducted by Prof. Torsten Vennemann at the Institute of Earth Surface Dynamics of UNILs Faculty of Geosciences and the Environment. These tests buttressed the earlier dating observations.

These replicas were made possible by the BRB’s purchase, in May 1868, of the last copies of the globes’ gores preserved on a flat sheet. The erstwhile Belgian finance minister, Jules Malou, ordered 200 facsimiles to be published by Merzbach-Falk in Brussels. A few other replicas of the globes were made at the same time. Unfortunately their exact number is not known, but a pair were given by Malou to his history society in 1877.

It was reasonable to think of the 1875 facsimiles considering the excellent condition of the Lausanne globes’ spheres compared with their much older-looking stands. But, in the end, this possibility was ruled out by the analyses performed on the spheres themselves. The UNIL globes were not made in the period around 1875.

While we already knew in early 2013 that the stands were made of 16th-century materials, our team still wanted the opinion of an expert. We therefore invited Dr Peter van der Krogt, a cartography historian and expert on 16th- and 17th-century Dutch globes at the Universities of Amsterdam and Utrecht, to come in spring 2013 and examine the Lausanne globes in situ. We took the opportunity to sound him out on various historical and practical issues.

The question of the globes’ authenticity was raised in view of the very different apparent state of the stands and the spheres. Even knowing that C₁₄ dating had already authenticated the stands, a visual examination could not entirely dispel uncertainty about the spheres.

Obviously these were not modern copies, but their remarkably good condition cast doubt on their origin. Could the spheres be from the series of facsimiles made in 1875 with the last remaining copies of Mercator’s gores ? More C₁₄ testing would clearly be needed to decide the issue one way or the other.

© Laurent Dubois, BCUL

© Laurent Dubois, BCUL

Dendrochronological certification was conducted as a prelude to C₁₄ radiocarbon dating of fragments of wood taken from the stands of the terrestrial and celestial globes. This certification was meant to ensure that the samples were relevant for the analyses.

The samples were drawn in 2012 by Jean Tercier and Jean-Pierre Hurni of the West Swiss Laboratory of Dendrochronology in Moudon, who also directed the C₁₄ dating performed by Dr Irka Hajdas at the ETH Laboratory for Ion Beam Physics, Radiocarbon Dating in Zurich.

Terrestrial globeCelestial globe

Ill. Rapport LRD

A sample was taken from the stand of the terrestrial globe on 23 August 2012 in BCUL-D’s storerooms. Of the stand’s four oak planks, two looked ancient whereas the wood of other two was lighter coloured and seemed more recent. It was therefore obvious that the stand had been restored. A 3 mm³ fragment was removed with a cutter from one of the two older-looking planks.

About 45 growth rings were counted on this plank. There was no sapwood signalling the proximity of the bark. The fragment came from a ring close to the heart of the tree, at about 42 rings from the outermost one of the plank. These observations made it possible to further pinpoint the date the tree was cut down.

The oak tree was felled at least 67 years after the date of the growth ring given by radiocarbon testing (42 years since the growth ring that was analysed, plus at least 25 more rings for the missing sapwood).

Dendrochronological dating yielded the following result :
Tree felled	1527-1707	probability 95.4%
C14 radiocarbon dating yielded the following result :
Wood from stand	1460-1640	probability 95.4%

Ill. Rapport LRD

Un prélèvement sur le socle du globe céleste est effectué le 23 août 2012 dans les dépôts de la BCUL à Dorigny. Le fragment de 3 mm³ a été retiré à l’aide d’un cutter sur l’une des trois planches en chêne du socle.

Sur cette planche, environ 60 cernes de croissance ont été décomptés, dont 6 cernes d’aubier. L’aubier présente une teinte plus claire que le bois de coeur. Il est situé à la périphérie du tronc, sa présence indiquant la proximité de l’écorce. Le fragment provient d’un cerne proche du coeur de l’arbre, à environ 55 cernes du cerne de croissance le plus extérieur de l’aubier. Ces observations permettent d’affiner les résultats pour approcher au plus près la date d’abattage de l’arbre.

L’abattage du chêne est d’environ 75 ans plus récent que la date du cerne analysé par le radiocarbone (55 années depuis le cerne analysé, auxquelles s’ajoutent 20 cernes d’aubier manquant).

Dendrochronological dating yielded the following result :
Tree felled	1485-1525	probability 95,4%
C14 radiocarbon dating yielded the following result :
Wood from stand	1410-1450	probability 95,4%/small>