Prof. W. A. Norton on the Physical Constitution of the Sun. 55 



The question suggests itself whether, by improvement of the 

 construction, this principle might not be made practically avail- 

 able in those cases where a uniform current (without successive 

 inversions) is desirable, as afforded by a voltaic battery. 



It may be remarked that in the figure a portion of the cur- 

 rent finds a circuit within the disk itself; this, however, may be 

 avoided by a change in the details of construction, as is the case 

 with the apparatus of Ampere, which shows the electrodynamic 

 rotation of a current. 



The theoretic interest of the question will not, I think, be 

 disputed, the converse principle (that is, the theory of the di- 

 rect production of motion from electricity) being dealt with in 

 every work professing to contain the principles of the science. 



PS. — Since this paper was written I have been informed by 

 Mr. C. F. Varley, to whom the subject treated of was com- 

 municated, that to his knowledge this question has been con- 

 sidered mathematically by Sir William Thomson. I am not* 

 however, aware that any paper on the subject has been pub- 

 lished. I trust, therefore, that this communication may be 

 found not unsuited for insertion in your valuable pages . 



London, June 12, 1871. 



VI. On the Physical Constitution of the Sun. 

 By Professor W. A. Norton*. 



AMONG the recent theories of the Physical Constitution of 

 the Sun, based on the later discoveries, astronomical and 

 spectroscopic, that propounded a few years since by M. Fayef 

 has been most favourably received. It is an essential feature of 

 this theory that the sun's mass consists wholly, or in a great 

 degree, of gases or vapours, and that a process of interchange 

 of solar matter between the interior and the photosphere is in 

 incessant operation, in ascending and descending currents, by 

 which the solar radiation is maintained. In a paper by J. 

 Homer Lane " On the Theoretical Temperature of the Sun, &c./' 

 published in Silliman's Journal, July 1869,it is elaborately argued, 

 and appears to be successfully maintained, that the great rapidity 

 of circulation required by this theory cannot subsist consistently 

 with the received laws of gaseous circulation. Quite recently 

 another theory of the sun's physical constitution has been prOr 

 pounded by Professor P. Zollner, of Leipzig — based mainly on 

 the well-established fact that the solar protuberances, conspicu- 



* From Silliman's American Journal for June 1871. 

 f Comptes Rendus, vol. lx. pp. 89 and 138. 



