48 



Mr. Airy — Analysis of 177 Magnetic Storms. [Dec. 17, 



The foregoing research was finished many months ago, but I delayed 

 pubhshing it in the hope of being able to announce at the same time the 

 formation of lactic acid by a similar process. I find, however, from the 

 * Annalen der Chemie und Pharmacie ' of last month that I have been 

 anticipated by "Wislicenus, who has succeeded in forming lactic acid in the 

 manner I have just described* 



December 17, 1863. 

 Major-General SABINE^ President, in the Chair. 



The following communications were read : — 



1. " First Analysis of 177 Magnetic Storms^ registered by the 

 Magnetic Instruments in the Royal Observatory, Greenwich, 

 from 1841 to 1857.^^ By George Biddell Airy, Astronomer 

 Royal. Received November 28, 1863. 



(Abstract.) 



The author first refers to his paper in the Philosophical Transactions, 

 1863, "On the Diurnal Inequalities of Terrestrial Magnetism as deduced 

 from Observations made at the Royal Observatory, Greenwich, from 1841 

 to 1857." These results were obtained by excluding the observations of 

 certain days of great magnetic disturbance ; it is the object of the present 

 paper to investigate the results which can be deduced from these omitted 

 days. 



The author states his reasons for departing from methods of reduction 

 which have been extensively used, insisting particularly on the necessity of 

 treating every magnetic storm as a coherent whole. And he thinks that 

 our attention ought to be given, in the first instance, to the devising of 

 methods by which the complicated registers of each storm, separately con- 

 sidered, can be rendered manageable ; and in the next place, to the discus- 

 sion of the laws of disturbance which they may aid to reveal to us, and to 

 the ascertaining of their effects on the general means in which they ought 

 to be included. 



The author then describes the numerical process (of very simple cha- 

 racter) by which, when the photographic ordinates have been converted 

 into numbers, any storm can be separated into two parts, one consisting of 

 waves of long period, and the other consisting of irregularities of much 

 more rapid recurrence. He uses the term " Fluctuation " in a technical 

 sense, to denote the area of a wave-curve between the limits at which the 

 wave-ordinate vanishes. The Waves, Fluctuations, and Irregularities, as 

 inferred from separate treatment of each storm, constitute the materials 

 from which the further results of the paper are derived. 



Table I. exhibits the Algebraic Sum of Fluctuations for each storm, with 

 the Algebraic Mean of Disturbances, and Tables II. and III. exhibit the 



