1869.] of some periods of Declination Disturbance at Lisbon. 239 



We also see that the greatest number of repetitions belong to the night 

 hours, that is to say, those hours when the movements of the needle 

 are easterly. In the morning hours there do not appear to be any well- 

 marked repetitions. 



I append examples chosen from the five years complete (July 1863 to 

 June 1868) of the declination curves of the Observatory at Lisbon (see 

 Plates V. & VI.). 



A greater number of cases might be quoted, but those I have chosen 

 are sufficient for our purpose. 



Meanwhile I must mention that, in the majority of instances, where no 

 relation apparently exists between one disturbance and the disturbances of 

 the days preceding and following, the disturbances are generally violent. 



There are twenty-four examples, fifteen of which show repetition on two 

 days, eight on three days, and one only where the curve appears repeated 

 for four days. 



In order that the identity may be easily recognized, I have placed the 

 curves with their corresponding periods vertical, the hours being marked 

 on each curve. 



It appears that all the facts exhibited in these examples agree with the 

 cosmical theory ; the cause (existing in the sun or in space) appears to 

 continue sometimes during two, three, or several days without undergoing 

 remarkable transformations. 



The repetition, being sometimes earlier, sometimes later, seems also to 

 indicate that the cause possesses a proper movement ; the cause persists, 

 but only comes again into operation when the earth by its diurnal rotation 

 is placed in a similar position or conjunction to that of the preceding days. 



It would be very curious to analyze the photographs of the sun so as to 

 see if there were any spots in the days of the examples, and if these spots 

 remained without sensible alteration during the days when the disturbances 

 remained so similar. 



BemarJis by B. Stewart. 



I have compared Senhor Capello's curves with the corresponding traces 

 of the declination at Kew, and it would appear that the Lisbon disturb- 

 ances are almost invariably reproduced at Kew at the same time, only to a 

 greater extent. It would further appear that the same amount of similarity 

 which the various Lisbon curves exhibit is also exhibited in the corre- 

 sponding Kew curves. 



Opinions may differ with regard to the strength of the evidence exhi- 

 bited by Senhor Capello in support of the peculiar action of the disturbing 

 forces of which he is an advocate. It would appear to me that the 

 strongest point in favour of the hypothesis is not so much the repetition 

 of a single disturbance as the repetition of a complicated disturbance in 

 most if not all of its sinuosities. Several examples of this occur in these 

 diagrams. 



