Prof. Powell on the Dispersion of Light. 261 



right; and a grete hole theirin, whereof the flawme cam oute 

 ot. And after a vj or vjj dayes it aroose North-Est, and so 

 bakkere and bakkere, and so enduryd a xiijj nj^o^htes full 

 lytell chaungynge, goyngefrom the North- Este to th'e Weste ; 

 and sometyme it wuld seme a quenched oute, and sodanly it 

 brent fervently ageyn. And then it was at one tynie playne 

 northe, and then it compassed rounde aboute the lode sterre, 

 for in the evynynge the blase went ageyns the Southe. And 

 m the mornynge playne northe, and then afterward West, 

 and so more West flamyng vpryght, and so the sterre con- 

 tynued nij wekys tylle the xx day of ffeveryere ; and when it 

 appered West in the fyrmament, then it lasted alle the nyo-ht, 

 somewhat discendyng with a grettere smoke on the hey re' 

 and som men seyd that the blassynges of the seide sterre 

 was of a myle lengh ; and a xjj dayes afore the vanyschyno-e 

 therof, It appereryd in the evenyng, and was down anon 

 withm two oures, and evyr of a colour pale stedfast, and it 

 kept his course rysynge west in the northe, and so every 

 nyght It apperid lasse and lasse tyll it was as lytell as a hesyll 

 styke, and so at the laste it vanesched away the xx day of 

 ffebruarii. And some men saide that this sterre was seen ii 

 or lij oures afore the sunne rysynge in Decembre iijj days 

 before Chrystynmasse in the Southwest, so by that reasoune 

 It compassed rounde abowte alle theerthe alleway chaunaynfj 

 his cours as is afore rehersid." 



The observationsof Johannes Regiomontanus upon the same 

 comet are recorded in the Nuremberg Chronicle. Wark- 

 worth's description was lately commuicated to the Society of 

 Antiquaries by my friend Mr. Bruce, and my object in send- 

 ing It to you was to afford an opportunity for those of your 

 readers to peruse it who are not likely to meet with it through 

 any other source. Your obedient servant, 

 J. O. Halliwell. 



XLII. Observations on some points in the Theory of the 

 Dispersion of Light. Bij the Rev. Baden Powell, M.A., 

 F.R.S., F.G.S., F.R.A.S., Savillian Professor of Geometry, 

 Oxford* ^ 



'jpHE problem of the dispersion was, for a long time, con- 

 fessedly the opprobrium of all theories of light, but 

 more especially, in proportion to its higher pretensions,— of 

 the undulatory, not simply because it had not explained those 

 phajnomena, but because, according to the received views, it 

 was at variance with them. It has only been within the last 

 few years, that, by a modification of the principles of this 

 • Communicated by the Author. 



