Decoding chancery records from the 1240s

Abstract

The English records from the 1240s contain many references to the purchase of gold on behalf of the king, Henry III. For example, the Liberate Rolls give explicit numerical information about the amounts of gold purchased and the price paid for it. These records also contain implicit information, and this can sometimes be extracted by analysing the arithmetical procedures that were used by the king's officials. We shall see how the purity of the gold was assessed, and how the price varied in consequence. The records occasionally mention gold in the form of coins, and in such cases our method can be used to identify the type of coin involved. Since there is little evidence about the methods used to perform the calculations, we shall consider the extent to which the Hindu-Arabic methods popularized by Leonard of Pisa (Fibonacci) were being adopted in England in the thirteenth century.

Acknowledgement

The author is grateful to an anonymous referee for a very helpful review, which resulted in significant improvements to the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 The record is quoted in the form published in the Calendar of the Liberate Rolls, Henry III Vol. II, 1240–1245 (Chapman 1930). References to this volume will be cited here in the form (C 000). The original roll used the customary language and notation of the thirteenth century, Latin text and Roman numerals.

2 Indeed, the system of public-key cryptography that is now used to keep data secure is based on that same observation.

3 For the history of assaying gold, see (Oddy 1983). In the early 1600s Thomas Harriot began using hydrostatic methods to check the fineness of English gold coins (Biggs 2019).

4 Most of the numbers quoted in this article can be checked independently, because the issue rolls corresponding to writs of liberate for 1241–42 have also been printed (Stacey 1992).

5 The Calendar has a footnote remarking on this feature, but it is misleading. There was no such thing as a ‘gold penny’ in 1242. See Section 6.

6 According to the Tractatus (Johnson 1956) the number 24 was also important in the assay of silver. Since there were 24 grains in a pennyweight, the sample to be assayed should weigh exactly 10 pennyweights, so that (in money terms) each grain represented one penny in a pound.

7 An account of Gerbert’s abacus can be found in the document known as Manuscript 17, from St John’s College, Oxford, available online at digital.library.mcgill.calms-17. The Bodleian Library has several manuscripts with relevant information; see for example Ms.Bodleian.Auct.F.1.9.f65v.

8 A printed edition of Fibonacci’s Latin manuscript was published by Boncompagni (1857) and an English translation is now available (Sigler 2002). It must be noted that, although Fibonacci used the decimal place-value system of representing numbers, his methods of calculating with them were not the same as the ones (such as ‘long division’) that were taught to children in the nineteenth and twentieth centuries.

9 The pounds, shillings, and pence were the Pisan kind, which were related in the same way as the English kind, but differed in value (Sigler 2002, 129). Some care is needed in interpreting Sigler’s translation.

10 Edward I had several reasons for employing the Italians, including the fact that they represented his bankers (Biggs 2020).