7 
Ordinary Meeting, October 18th, 1870. 
E. VV. Binney, F.R.S., F.G.S., President, in the Chair. 
Professor Balfour Stewart, F.R.S., exhibited a series of 
sun-spot curves projected from results obtained by himself 
and Mr. De la Rue, from observations of Schwabe, Carring- 
ton, and the Kew series of photographs of the sun. These 
extend over a term of about 40 years, and exhibit a principal 
and secondary maximum and minimum in each solar spot 
period of 1 1 years, thus corresponding with the light curves of 
R Sagittae observed by Mr. Baxendell, and j3 Lyras by Prof. 
Argelander. Mence it may possibly be that notwithstanding 
the darkening of the sun’s surface during the maximum 
spot period, the total light and heat emitted by -the sun at 
this period is really greater than at the times of minimum 
spot frequency. 
Mr. Lockyer, F.R.S., gave an account of his recent spec- 
troscopic investigations of the solar atmosphere, and pointed 
out that the conclusions arrived at by De la Rue, Stewart, 
and Loewy confirmed the views to which he himself had 
been led by spectroscopic observations of the sun during 
the last tv T o or three years. These tended to show that the 
absorbing atmosphere, termed the chromosphere, which he 
had proved to exist round the sun’s body, had gradually 
diminished in thickness since the last solar spot minimum 
in 1867. 
Mr. Boyd Dawkins, F.R.S., gave a short account of the 
examination of Offa’s Dyke made in the autumn by Col. 
Lane Fox and himself. The portion examined extended 
from Cherbury in the south to the abrupt range of limestone 
hills to the north of Llanamynech. At Nantcribba Hall, 
Proceedings — Lit. & Phil. Soc.— Vol. X. — No. 2 . — Session 1870-71. 
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