175 



finding that the observations of these years confirm every deduction 

 which he had ventured to make from the analysis of the disturbances 

 of the former period ; w^hilst new and important features have pre- 

 sented themselves in the comparison of the frequency and amount 

 of the disturbances in different years, apparently indicating the 

 existence of a periodical variation, which, either from a real or causal 

 connection, or by a singular coincidence, corresponds precisely, both 

 in period and epoch, with the variation in the frequency and magni- 

 tude of the solar spots, recently announced by M. Schv/abe as the 

 result of his systematic and long-continued observations. 



The method pursued in examining the laws of the Declination- 

 disturbances in 1846, 47, 48, is the same as that adopted in the three 

 preceding years. Every hourly observation which was found to 

 differ a certain amount from the mean value of the Declination in 

 the same month and at the same hour was, as before, separated from 

 the rest. The number of observations thus separated in the period 

 commencing July 1, 1843, and ending July 1, 1848, was at Toronto 

 3940, and at Hobarton 3469, being respectively 1 in 9*43 at Toronto, 

 and 1 in 10*55 at Hobarton, of the whole number of hourly observa- 

 tions. The disturbed observations being distributed into the several 

 hours, months, and years in which they had occurred, their numbers 

 and aggregate values in each particular hour, month, and year, were 

 ascertained. They were then divided into easterly and westerly deflec- 

 tions, and the same process of distribution was gone through with each 

 of the divisions. The mean hourly, monthly and yearly number and 

 aggregate values in the whole period were then taken as the respec- 

 tive units, and the ratios to these units computed for each of the hours, 

 months and years ; whereby the relations, whether of numbers or 

 of aggregate values in diff*erent hours, different months, and different 

 years, were shown. 



The results thus obtained are discussed separately in the follow- 

 ing order : — 



I. Inequality or variation in the number and aggregate values of 

 the disturbed observations in different hours. This examination is 

 made by classing together — 1st, easterly disturbances at Toronto 

 and westerly at Hobarton ; and 2nd, westerly at Toronto and east- 

 erly at Hobarton. 



From the first classification, it appears that at both stations there 

 are fewer disturbances, and their aggregate values are less in the 

 hours of the day than in those of the night ; that 9 p.m. is the hour 

 of the maximum of frequency and also of value at Toronto, and 

 11 P.M. at Hobarton ; and that the periods of minima are between 

 2 and 3 p.m. at Toronto, and between 5 and 6 a.m. at Hobarton. 

 It appears further that the average value has a similar law of varia- 

 tion to that of the number and aggregate value. 



The second classification shows that at Hobarton the contrast both 

 in frequency and aggregate value is still between the hours of 

 the day and those of the night, the ratios being, however, in this 

 case greater than unity during the former hours, and less than unity 

 during the latter, contrary to what takes with the easterly disturb- 



