Royal Society. 235 



from 0'60 in 1843 to 1*43 in 1848, and the ratio of the value from 

 0"52 in 1843 to 1*51 in 1848, the variation in each having much 

 more the aspect of a periodical inequality than of an accidental va- 

 riation. Looking to the theoretical importance of the existence of 

 a periodical inequality of this nature, affecting at tlie same time, and 

 in the same manner, parts of the globe most remote from each other, 

 the author refers to the confirmation it may obtain from contempora- 

 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 support 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. Lament from the 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 IMS 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 two 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 sun is in the northern or the southeni 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 jirogressive 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- 



