Royal Society. 233 



From the discussion of the magnetic observations made at Toronto 

 and Hobarton in the years 1843, 44, 45, the author in a former 

 paper adduced evidence of the existence of periodical laws by which 

 the principal disturbances of the magnetic declination appeared to 

 be regulated. Having since had occasion to examine the disturb- 

 ances of the Declination at the same two stations in the three suc- 

 ceeding years 1846, 47, 48, he states that he had the satisfaction of 

 finding that the observations of these 3'ears confirm every deduction 

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

 of the former period ; whilst new and important features have pre- 

 sented themselves in the comparison of the frequency and amount 

 of the disturbances in different yeat's, 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 tlie solar spots, recently announced by M. Schwabe 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 resi^ectively 1 in 9'43 at Toronto, 

 and 1 in 10'55 at Hobarton, of the whole number of hourly obsei*va- 

 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 dividedinto easterly and westerly deflec- 

 tions, and the same process of distributionwas 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, Avhether of numbers or 

 of aggregate values in different 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 apj)ears 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 arc between 

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



