MAGNETIC DECLINATION AT KEW AND NERTSCHINSK. 
237 
giving reason to infer that, by subjecting the disturbances to a more searching analysis, 
systematic progressions indicative of two or more distinct sources of disturbance in each 
hemisphere might be made to disclose themselves. 
It had been found, moreover, that at every station where the examination had been 
made the disturbances of the declination were occasionally deflections to the East, and 
occasionally deflections to the West, from the mean position of the magnet; and those of 
the Dip, and of the total Force, occasionally increasing and occasionally decreasing the 
mean values. The aggregate amounts of disturbance in each element were now there- 
fore separated into distinct categories, and the ratios of disturbance at the several hours 
in each category to the mean hourly ratios were determined by a process similar to that 
adopted in the analysis of the aggregate values. The results fully justified the labour 
expended in this proceeding ; each category presented progressions still more systematic 
and of much greater simplicity than had appeared in the preceding investigation pre- 
vious to which the categories had not been separated ; giving great probability to the 
inference that at every station a similar process would manifest that there were at least 
two, and probably only two, distinct sources in each hemisphere, to which disturbances 
occurring simultaneously might be ascribed ; and that by an increase in the number of 
stations, particularly if they were judiciously selected, the geographical localities in which 
the greater part at least of the disturbances originated, might be approximately traced. 
Confining ourselves, for brevity, to the illustration afforded by a single element, viz. the 
Declination, it was found that at all stations, in all parts of the globe, the disturbances 
of the declination resolved themselves into two distinct and dissimilar categories ; the same 
two distinct and dissimilar forms of diurnal progression being everywhere reproduced 
with little other variation than that of the particular hours of maxima and minima ; but 
having this additional important peculiarity, that the particular form of the curve of 
the diurnal progression which characterized the Easterly Deflection at certain stations 
marked the Westerly Deflection at certain other stations, and vice versd. It was also 
found that at some stations the Easterly Deflections greatly preponderated over the 
Westerly, whilst at other stations the Westerly were predominant. An attentive con- 
sideration of the facts elicited by this extensive though somewhat laborious investiga- 
tion strengthened the previously prevailing impression, that the progressive increase of 
our knowledge of these remarkable phenomena would lead, in both hemispheres, to 
the establishment of a connexion — if not to the identification — of the terrestrial sources 
of the casual and transitory disturbances with the foci, as they are sometimes called, of 
the two magnetic systems of the globe. 
Proceeding from these premises, it appeared desirable to examine whether, if two 
stations were taken in a suitable and nearly similar latitude, v one of which might be on 
the eastern and the other on the western side of one of the supposed points of terrestrial 
origin, and if a sufficient comparison were made of the disturbances simultaneously 
observed at the two stations, the category of easterly deflections at the one station might 
not be found to correspond in the form of the curve, and possibly also in the hours of 
2x2 
