454 Prof. Wanklyn on the Action of Sodium 



cloud permanently established at a sufficient height in their at- 

 mospheres, the cloud must act as a carrier of heat and raise the 

 layer of hydrogen in which it floats to incandescence, while the 

 adjoining strata on both sides remain cool. The cloud might be 

 of any of the kinds enumerated in §§ 69 & 71 of my paper "On 

 the Constitution of the Sun." And if the stellar atmosphere 

 extend far outside the stratum of cloud, we may expect to find a 

 dark absorption-band in the middle of each of the four bright 

 hydrogen lines of these stars. 



Appendix. 



I would wish to take this opportunity of asking the reader to 

 correct two errors in my previous papers. In a paper " On the 

 Internal Motions of Gases compared with the Motions of Waves 

 of Light," Phil. Mag. for August 1868, in the last line of § 2, 

 for 16 2 or upwards of 250 times read ^16 times. And in the 

 paper "On. the Physical Constitution of the Sun and Stars" 

 cancel the footnote to § 28 (Proceedings of the lloyal Societv, 

 vol. xvii. pp. 20 &21). 



From a review of the additional iron lines seen by Angstrom 

 with a continuous electric current, his account of which* I have 

 succeeded in procuring within the last month, it is manifest that 

 the cause of their not being seen in the spark from RuhmkorfPs 

 machine is in most cases not what I conjectured in the footnote, 

 but a purely physiological phenomenon. The spark is so evan- 

 escent (lasting only one three-thousandth, or thereabouts, of the 

 time required to make the maximum impression on the retina) 

 that no lines which are not of the exalted intensity that will com- 

 pensate for this can be seen. It is evident, therefore, that a 

 vastly feebler continuous current may reveal multitudes of lines 

 not visible to our eyes in the spark. 



LVI. On the Action of Sodium on Valerianic Ether. By J. 

 Alfred Wanklyn, Professor of Chemistry in the London Jn- 

 stitution-f. 



~^HE ethers of the fatty acids were among the very first or- 

 ganic compounds to be submitted to the action of potas- 

 sium and sodium. Lowig and Weidmann's paper describing 

 researches on the action of the alkali-metals on these ethers was 

 published in tiie year 1840. The results arrived at, although 



* On the Fraunhofer Lines, together with a diagram of the violet part 



of the Spectrum, by A. J. Angstrom and R. Thalen. Published by W. 

 Schultz of Upsala. 

 t Communicated bv the Author. 



