On the Elevientary Colours of the Spectrum. 489 



dary effect, arising from the polarizing influence of tlie asthereal 

 waves upon the gethereo-ponderable atoms of the wire. 



Such waves pass superficially in preference ; but when the 

 wire is comparatively small, the reaction between the waves 

 and aethereo-ponderable atoms becomes sufficiently powerful 

 to polarize them, and thus render them competent, for an ex- 

 tremely minute period of time, to produce all the affections of 

 a galvano-electric current, whether of ignition, of electrolysis, 

 or magnetization. Thus, as the aethereo-ponderable waves 

 produce such as are purely aethereal, so purely aethereai waves 

 may produce such as are aethereo-ponderable. 



The polarization of hair upon electrified scalps is supposed 

 to be due to a superficial association with the surrounding 

 polarized aethereal atoms, while that of iron filings, by a mag- 

 net or galvanized wire, is conceived to arise from the influence 

 of polarized aethereo-ponderable atoms, consisting of aethereal 

 and ponderable matter in a state of combination. 



Faradian discharges are as truly the effects of aethereo- 

 ponderable polarization, as those from an electrified conductor, 

 or coated surfaces of glass are due to static aethereal polariza- 

 tion (39, 40, 41) ; last paragraph, note, page 485. 



It is well known that if a rod of iron be included in a coil of coated cop- 

 per wire on making the coil the medium of a voltaic discharge, the wire is 

 magnetized. Anreeably to a communication from Joule, in the Phil. Mag. 

 and Journ. for Feb. 1847, the bar is at the same time lengthened without 

 any augmentation of bulk ; so that its other dimensions must be lessened 

 iu proportion to the elongation. 



All these facts tend to prove that a change in the relative position of the 

 constituent aethereo-ponderable atoms of iron accompanies its magnetiza- 

 tion, either as an immediate cause, or as a collateral effect. 



LXIV. Observations on the Elementary Colours of the Spec- 

 trum, in reply to M. Melloni. By Sir David Bkewster, 

 K.H., D.C.L., F.R.S., and V.P.ILS. Edinfi^ 



IT is with considerable reluctance that I have been induced 

 to notice the criticisms of M. Melloni, on my Analysis of 

 the Spectrum, which occupy so large a portion of his paper 

 published in the Phil. Mag. lor April last. Had these criti- 

 cisms emanated from any inferior person, I should have re- 

 garded them as sufficiently refuted by the few remarks which 

 I made on the analogous observations of Dr. Draper. The 

 high and well-merited reputation, however, of M. Melloni, 

 and the singular confidence which he seems to place in his 

 own results, render it necessary that I should do more than 



* Communicated by the Author. 



