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American Continent, and to the Southern Hemisphere and the 

 Tropics, may first be disposed of in a very few words. The contem- 

 poraneous character of the disturbances, which had been shown by 

 the German term-observations to extend over the larger portion of the 

 European Continent, manifested itself also in the comparisons of the 

 term-days in 1840, 1841, and 1842 at Prague andBreslau in Europe, 

 and Toronto and Philadelphia in America, published in 1845; and 

 the same conclusion was obtained by comparing with each other the 

 term-days at the Colonial Observatories, situated in parts of the globe 

 most distant from one another. The days of disturbance still appeared 

 to be of casual occurrence, but were now recognized as affections com- 

 mon to the whole globe, showing themselves simultaneously at stations 

 most widely removed from each other. When distant stations were 

 compared, as for example stations in Europe with those in America, 

 and either or both with Tasmania, discrepancies in the amount of par- 

 ticular perturbations, similar to those which had been found in com- 

 paring the European stations with each other, presented themselves, 

 but larger and more frequent, and extending occasionally even to the 

 reversal of the direction of the simultaneous disturbance. Instances 

 were not unfrequent of the same element, or of different elements, 

 being disturbed at the same observation-instant in Europe and 

 America ; and on the other hand, there were perturbations, sometimes 

 of considerable magnitude, on the one continent, of which no trace 

 was visible on the other. Hence it was concluded, with the increased 

 confidence due to this additional and more extensive experience, 

 that various forces proceeding from different sources were contem- 

 poraneously in action; and it was further inferred that the most 

 suitable and promising mode of pursuing the investigation was by an 

 endeavour to analyse the effects produced at individual stations, and 

 to resolve them if possible into their respective constituents. 



The hourly observations which had been commenced at the 

 Colonial stations in 1841 and 1842, and continued through several 

 subsequent years, furnished suitable materials for this investigation, 

 the first fruits of which were the discovery, that the disturbances, 

 though casual in the times of their occurrence, and most irregular 

 when individual perturbations only were regarded, were, in their 

 mean effects, strictly periodical phenomena ; conforming in each 

 element, and at each station, on a mean of many days, to a law de-* 



