372 Rev. S. J. Perry and Prof. Balfour Stewart. [Dec. 10, 



Table II will explain itself. In it we have embodied the various 

 individual observations of Table I, with the following exceptions : — 



On account of apparently On account of the duration 



unequal duration. being under five minutes. 



No. 3 No. 10 



„ 9 „ 11 



» 15 „ 12 



„ 17 „ 21 



„ 18 „ 28 



„ 33 „ 32 



„ 56 „ 34 



„ 64 „ 42 



„ 65 „ 54 



„ 66 „ 68 



„ 71 „ 69 



„ 76 ,,107 



„ 84 



„ 88 



„ 95 



„ 96 



From Table 11 we may dednce the following conclusions: — 



(1.) In the very great majority of cases the angular value of the decli- 

 nation disturbance is greater for Stonyhurst than for Kew. 

 S 



(2.) The ratio — is certainly greater for disturbances of short than for 



those of long duration. Our observations are not, however, suffi- 

 ciently extensive to enable us to represent this ratio graphically as 

 a function of the duration. 

 (3.) As far as we can tell from a limited number of observations the 

 value of the above ratio does not depend on the magnitude of the 

 disturbance. 



We trust to make on a future occasion a more complete comparison 

 between the simultaneous magnetic fluctuations as derived from the 

 curves of the two observatories. 



Note. — It might be desirable to add a few words in fuller explanation of the 



method adopted. 



This method is founded on the implied belief that disturbances are indications of 

 the way in which the magnetic earth rights itself with regard to the forces acting 

 upon it. Our experience is that such disturbances never occur singly, but very 

 frequently as couplets or sets of couplets. There is no such thing as a magnetic 

 tableland separated from another by a single slope. We have rather a rise and 

 then a fall, or it may be a fall and then a rise, and in the end the state of things, 

 after the disturbance has run its course, is not greatly different from that before it 

 began. This duality, as well as the results of this paper, would lead us to imagine 



