745. _At his large_, unrestrained, free to move. Cf. _at thy large_, Cant. Ta., A 1283, 1292. 746. _Charge_, a heavy weight, opposed to _light thing_. The verb _seke_ is understood from l. 744. 'A light thing (seeks to go) up, and a weight (tends) downwards.' In Tyrwhitt's glossary, the word _charge_, in this passage, is described as being a verb, with the sense 'to weigh, to incline on account of weight.' How this can be made to suit the context, I cannot understand. _Charge_ occurs as a sb. several times in Chaucer, but chiefly with the secondary sense of 'importance'; see Kn. Tale, A 1284, 2287; Can. Yem. Ta., G 749. In the Clerkes Tale, E 163, it means 'weight,' nearly as here. 750. _Skilles_, reasons. The above 'reasons' prove nothing whatever as regards the fish in the sea, or the trees in the earth; but the eagle's mode of reasoning must not be too closely enquired into. The fault is not Chaucer's, but arises from the extremely imperfect state of science in the middle ages. Chaucer had to accept the usual account of the four elements, disposed, according to their weight, in four layers; earth being at the bottom, then water, then air, and lastly fire above the air. See the whole scheme in Gower, Conf. Amant. bk. vii.; ed. Pauli, ii. 104: or Popular Treatises on Science, ed. Wright, p. 134. 752. See Chaucer's tr. of Boethius, bk. iii. pr. 11, l. 72. Hence Boethius is one of the 'clerkes' referred to in l. 760. 759. Dante mentions these two; Inf. iv. 131-4. 765. So also in Cant. Tales, D 2233:-- 'every soun Nis but of eir reverberacioun, And ever it wasteth lyte and lyte awey.' The theory of sound is treated of in Vincent of Beauvais, Speculum Naturale, lib. iv. c. 14. The ancients seem to have understood that sound is due to the vibration of the air; see ll. 775, 779. Thus, in the treatise by Boethius, De Musica (to which Chaucer expressly refers in Non. Preest. Tale, B 4484), lib. i. c. 3, I find:--'Sonus vero præter quendam pulsum percussionemque non redditur.... Idcirco definitur sonus, aeris percussio indissoluta usque ad auditum.' 788. _Experience_, i.e. experiment. The illustration is a good one; I have no doubt that it is obtained, directly or at secondhand, from Boethius. Vincent of Beauvais, Spec. Nat. lib. xxv. c. 58, says:--'Ad quod demonstrandum inducit idem Boetius tale exemplum: Lapis proiectus in medio stagni facit breuissimum circulum, et ille alium, et hoc fit donec vel ad ripas peruenerit vel impetus defecerit.' This merely gives the substance of what he says; it will be of interest to quote the original passage, from the treatise De Musica, lib. i. c. 14, which chapter I quote in full:--