1879.] 



Declination and Horizontal Force. 



45 



and horizontal force are subject to a periodical variation, the duration 

 of which is equal to that of the known eleven-year sun-spot period. 



2. That the epochs of minimum and maximum of magnetic and 

 sun-spot effect are nearly coincident; the magnetic epochs, on the whole, 

 occurring somewhat later than the corresponding sun-spot epochs. 

 The variations of duration in different periods appear to be similar for 

 both phenomena. 



3. That the occasional more sudden outbursts of magnetic and sun- 

 spot energy, extending sometimes over periods of several months, 

 appear to occur nearly simultaneously, and progress collaterally. 



4. That it seems probable that the annual inequalities of magnetic 

 diurnal range are subject also to periodical variation, being increased 

 at the time of a sun-spot maximum, when the mean diurnal range is 

 increased, and diminished at the time of a sun-spot minimum, when 

 the mean diurnal range is diminished. 



Conclusions Xos. 1, 2, and 3 appear to. be sufficiently certain, but 

 the evidence in favour of Xo. 4 is not so decisive, 



Hay 15, 1879. 



THE PEE SID EXT in the Chair. 



The Presents received were laid on the table and thanks ordered for 

 them. 



The following Papers were read : — 



I. ' ; Xote on a recent Communication by Messrs. Liveing and 

 Dewar." By J. Norman Lockyer, F.R.S. Received 

 April 30, 1879. 



In my paper of last December* I called attention to the importance 

 of discussing Young's observations of the chromospheric lines in con- 

 nexion with the spectra of the metallic elements. In subsequent 

 communications I have given preliminary results of this discussion so 

 far as it has already proceeded. 



Since my paper was read Messrs. Liveing and Dewar have, in a 

 paper printed in the last number of the " Proceedings," given a table 

 which professes to state the number of times various lines in certain 

 metals were seen by Young in connexion with certain reversal pheno- 

 mena observed by themselves. 



The statements, however, made in this table with regard to the 

 * "Proceedings." vol. xxyiii, p. 172. 



