Prof. B. Stewart and W. Dodgson. [May 29, 



III. Preliminary Keport to the Comnurtee on Solar Physics on 

 a Method of Detecting the Unknown Inequalities of a 

 Series of Observations." By Bai*fotjr Stewart, FJELS„ 

 Professor of Natural Philosophy in Owens College. Alan- 

 chester, and William Dodgsox. Communicated to the 

 Royal Society at the request of the Committee. Received 

 May 15. 1879. 



1. Our chief reason for suspecting the existence of a connexion 

 between the state of the solar surface (as this is revealed by spots) and 

 the magnetism and meteorology of the earth is derived from the fact 

 that our observational series of sun-spots, on the one hand, and of mag- 

 netical and meteorological changes, on the other, are believed to be all 

 subject to a co mm on me quality, whose period (about 11 years) is 

 virtually the same in all. But as it is only of late years that observa- 

 tions of great accuracy have been made in these three branches of 

 inquiry, it is impossible to compare together more than a few series of 

 long-period inequahty. and hence some observers are still inclined to 

 doubt the reality of a true connexion between the sun and the earth of 

 the kind above mentioned. We are thus led to ask ourselves whether 

 ther e may not be other fnequahties of shorter period in these various 

 observations, and whether we cannot devise some means of ascertaining 

 the exact periodical times of these as well as their other properties. 



We might thus expect to decide the question regarding a connexion 

 between these three branches, for if solar observations and those of 

 terrestrial magnetism and nieteorolo gy all exhibit a series of inequa- 

 lities that are essentially the same in each, it is impossible to call in 

 question the reality of some connexion between them. 



2. The researches of Broun. Homstein. BaxendelL and others have 

 indicated the probable existence of inequalities in magnetism and 

 meteorology, with periods of comparatively short length. Messrs. De 

 La Rue. Stewart, and Loewy nave likewise observed indications of a 

 short-period fluctuation in sun-spots : but we are not aware that any 

 attempt has yet been made to ascertain with great precision the exact 

 period or periods of unknown inequahties either in terrestrial or in 

 sun-spot observations. 



As our sun-spot records have not yet been rendered sufficiently com- 

 plete, it may be questioned whether the time has yet arrived for 

 attempting any such investigation with respect to them ; but our 

 records of observations in magnetism and meteorology are now so 

 long- continued and complete as to render it desirable in then- case to 

 make the attempt. This we have done in the following preliminary 

 investigation. 



We began first of all by making use of the records of the Kew 



