Brytte (Also Britte, Brit, or Brute), Walter

(fl, Oxford, England, second half of fourteenth century)

astronomy.

According to Brodrick,¹ Brytte was elected to a fellowship at Merton College in 1377, and in MS Digby 15 (fol. 96v) he is mentioned as quondam socius collegii de Merton. This is almost all we know about his life, except for an old tradition related by Wood² that he was a follower of John Wycliffe (Bachelor of Merton 1356) and author of the book De auferendis clero possessionibus. For this reason R. L. Poole³ and later A. B. Emden⁴ tentatively identified him with a layman who in 1391 was tried for heresy before the bishop of Hereford. Nothing has come to light to substantiate this, however, so we are left with the only work that can safely be ascribed to him: the treatise Theorica planetarum secundum dominum Walterum Brytte, with the incipit Circulus eccentricus, et egresse cuspidis, et ingredientis centri idem sunt, which is extant in at least eight manuscripts, four of which were identified by Bjørnbo.⁵

Many elementary manuals of planetary theory are known under the title Theorica planetarum, and Brytte’s treatise has often been confused not only with a similar text by an earlier Mertonian scholar, Simon Bredon (fellow 1330, d. 1372), but also with the extremely popular and much used “Old Theorica planetarum,” which has been ascribed to Gerard of Cremona and to many other authors but is actually an anonymous textbook written in the second half of the thirteenth century. Recent research has cleared up much of the confusion, with the result⁶ that although the “Old Theorica” certainly served as a prototype for Brytte, his work is neither a simple copy among several hundred others nor a commentary of the usual kind. It must be regarded as a revised version with strongly individual features. Of course, Brytte retained many of the notions current at his time, such as the “physical” doctrine of ethereal spheres as guidance mechanisms for the planets. On the other hand, he rearranged the traditional matter in a more logical way, dealing more fully with the theory of Venus and discarding the very confused chapter on latitudes in the “Old Theorica.”

The most interesting characteristic of the Theorica is Brytte’s obvious efforts to remedy some of the worst errors of the older text by means of his insight into kinematics, which clearly stemmed from the great Merton school of mechanics that flourished before and at the middle of the century. Where the “Old Theorica” spoke simply of “motion,” Brytte carefully distinguishes between “physical” (i.e., linear) velocity and “astronomical” (i.e., angular) velocity, just as he is familiar with both uniform and nonuniform motion and with the composition of angular velocities. These kinematic concepts are applied to planetary theory, with the consequence that Brytte, unlike the author of the old text, is able to state the correct condition for a planet’s being stationary: that the apparent angular velocity of the planet on the epicycle is equal but opposite to the angular velocity of the epicycle center on the deferent. Yet he is unable to deduce a correct geometrical construction from this principle, so that like most medieval astronomers, he determines the stationary points by means of tangents from the center of the earth to the epicycle. Thus his efforts to make the new kinematics useful to astronomy did not result in a correction of this persistent error in the elementary teaching of astronomy in the Middle Ages.⁷

NOTES

1. P. 219.

2. I, 475.

3. II, 1266.

4. Pp. 270–271.

5. Pp. 112 ff.

6. Pedersen, “The Theorica planetarum Literature,” pp. 225 ff.

7. An ed. of Brytte’s treatise by Pedersen is in press.

BIBLIOGRAPHY

The MSS of the Theorica planetarum are British Museum Egerton 847, 104v–122v, and Egerton 889, 7r–17r; and Bodleian Library Bodl. 300, 45r–53v; Digby 15, 58v–96v; Digby 48, 96r–112v; Digby 93, 37r–51v; Digby 98, 132r–145r; and Wood D.8, 93–112r. An edition of the Theorica is Pedersen, Theorica Planetarum. Texts and Studies in Mediaeval Astronomy (in press).

Works dealing with Brytte or the Theorica are A. A. Bjørnbo, “Walter Brytte’s Theorica planetarum,” in Biblioteca mathematica, 6 (1905), 112 ff.; G. H. Brodrick, Memorials of Merton College (Oxford, 1885), p. 219; A. B. Emden, A Biographical Register of the University of Oxford to A. D. 1500 (Oxford, 1957), I, 270 f.; Olaf Pedersen, “The Theorica planetarum Literature of the Middle Ages,” in Classica et mediaevalia, 23 (1962), 225 ff.; R. L. Poole, in Dictionary of National Biography, II, 1266; and Anthony à Wood, Antiquities of Oxford (Oxford, 1786), I, 475.

Olaf Pedersen