68 



Royal Society 



Barium, strontium, calcium in the flame of Bunsen's lamp show 

 bands like spectra of the first order, and in each case a well-defined 

 line-like spectra of the second order. On introducing chloride of 

 barium into an oxy hydrogen jet, the shading of the bands was resolved 

 into fine dark lines, proving that the band spectrum of barium is in 

 every respect a spectrum of the first order. 



Spectra of the first order were observed in the case of only a few 

 of the heavy metals, among which may be particularly mentioned lead, 

 which, when its chloride, bromide, iodide, or oxide was introduced 

 into an oxyhydrogen jet, gave a spectrum with bands which had a 

 channeled appearance in consequence of a shading by fine dark 

 lines. 



Chloride, bromide, and iodide of copper gave in a Bunsen's lamp, 

 or the oxyhydrogen jet, spectra with bands, and besides a few bright 

 lines. The bands in the three cases were not quite the same, but 

 differed from one another by additional bands. Manganese showed 

 a curious spectrum of the first order. "When an induction discharge 

 passed between electrodes of copper or of manganese, pure spectra of 

 these metals, of the second order, were obtained. 



March 17. — Major-General Sabine, President, in the Chair. 



The following communication was read : — 



"Remarks on Sun Spots." By Balfour Stewart, M.A., F.R.S., 

 Superintendent of the Kew Observatory. 



In the volume on Sun Spots which Carrington has recently pubj 

 fished, we are furnished with a curve denoting the relative frequency 

 of these phenomena from 1760 to the present time. This curve 

 exhibits a maximum corresponding to 1788*6. Again, in Dalton's 

 ' Meteorology ' we have a list of aurorse observed at Kendal and Kes- 

 wick from May 1786 to May 1793. 



The observations at Kendal were made by Dalton himself, and 

 those at Keswick by Crosthwaite. This list gives — 



For the year 1787 

 1788 

 1789 



. 27aurorae, 

 .53 „ 

 .45 „ 



For theyear 1790. . . . 36aurorse; 

 1791.... 37 „ 

 1792.... 23 „ 



showing a maximum about the middle, or near the end of 1788. 

 This corresponds very nearly with 1788*6, which we have seen is 

 one of Carrington's dates of maximum sun spots. 



The following observation is unconnected with the aurora borealis. 

 In examining the sun pictures taken with the Kew Heliograph under 

 the superintendence of Mr.De la Rue, it appears to be a nearly uni- 

 versal law that the faculae belonging to a spot appear to the left of 

 that spot, the motion due to the sun's rotation being across the pic- 

 ture from left to right. 



These pictures comprise a few taken in 1858, more in 1859, a few in 

 1861, and many more in 1862 and 1863, and they have been care- 

 fully examined by Mr. Beckley, of Kew Observatory, and myself 

 The following Table expresses the result obtained : — 



