17; 



neous observations at other stations. Pending such confirmations 

 he remarks that this progressive increase in the amount of disturb- 

 ance at Toronto and Hobarton, between the years 1843 and 1848, 

 derives great additional interest and importance from its apparent 

 connection with an equally remarkable progressive increase which 

 took place at the same two stations, in the magnitude of the diurnal 

 range of the Declination in the same years. From the mean magni* 

 tude of the diurnal variation of the Declination in each month, tables 

 are deduced showing the mean magnitude or ranges in the four 

 months constituting the respective seasons, and in the twelve months 

 constituting the year, in each year from 1843 to 1848, both at To- 

 ronto and at Hobarton. From these tables it appears that at each 

 station, for each of the seasons and for the whole year, the diurnal 

 range of the Declination had a progressive increase during that 

 period ; the increase for the whole year being from 8'" 90 in 1843 to 

 l2'-04 in 1848 at Toronto, and from 7 ''66 to ll'-43 at Hobarton. 

 In sujDport of the opinion that these progressive increases in the 

 range of the diurnal variation at two stations separated from each 

 other by nearly half the surface of the globe are independent and 

 corresponding measures of a general phenomenon, the author ad- 

 duces the results obtained by Dr. Lamont from tlie observations at 

 Munich. From these it appears that the mean range of the diurnal 

 variation in monthly periods at Munich increased progressively from 

 7-82 in 1843 to 11-15 in 1848. 



The author remarks that the increase so distinctly marked in the 

 two classes of phenomena between the years 1843 and 1848 tends 

 to indicate a causal connection subsisting between the disturbances 

 and the regular diurnal variation. If we suppose the diurnal varia- 

 tion to be divided into tvv^o portions, one of which is nearly uniform 

 in amount throughout the year (at the same station), whilst the 

 other has a hemispherical phase, developed in either hemisphere ac- 

 cording as the Sim is in the northern or the southern signs, — it is the 

 former of these two portions which sustains the variation consistent 

 with and apparently related to the variation in the number and values 

 of the disturbances. 



That the progressive increase in the mean monthly diurnal range, 

 from 1843 to 1848, was not confined at Toronto and Hobarton to 

 the Declination only, but took place likewise in the diurnal variations 

 of the Inclination and Total Force, is shown by the tables which are 

 given. 



In conclusion the author observes, that " in our present ignorance 

 of the physical agency by which the periodical magnetic variations 

 are produced, the possibility of the discovery of some cosmical con- 

 nection which may throw light on a subject as yet so obscure should 

 not be altogether overlooked. As the sun must be recognised as at 

 least the primary source of all magnetic variations which conform to 

 a law of local hours, it seems not unreasonable that in the case of 

 other variations also, whether of irregular occurrence or of longer 

 period, we should also look in the first instance to any periodical 

 variation by which we may learn that the sun is affected, to see 



