118 
COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
from the monthly means of the observations in the several months, from 8'’90 to 
12'’ 11 at one station, and from 7'‘66 to 10'’63 at another station separated from the 
former by nearly half the surface of the globe, might naturally have created an 
expectation that they would prove to be independent and corresponding measures of 
a general phenomenon. Fortunately, in the case of the diurnal range, we have not 
to wait, as we have in the case of the disturbance-progression, for a confirmation of 
its extension to Europe. In a recent number of Poggendorff’s Annalen, 1851, No. 
12, December 23 (which only reached the author of this paper when the greater 
part of it was already written). Dr. Lamont has published a Table of the mean 
monthly range of the diurnal variation of the Declination at Munich, from 1841 to 
1850 inclusive, from which he also has been led to infer the probable existence of a 
periodical inequality, having its epoch of minimum in 1843*5, and of maximum in 
1848*5. The mean range of the diurnal variation in monthly periods at Munich in 
the years discussed in this paper, is stated in Dr. Lamont’s communication to have 
been as follows : — 
1843 
7-15 
1844 
6*61 
1845 
8*13 
1846 
8*81 
1847 
9*55 
1848 
11*15 
The years which Dr. Lamont infers from the Munich observations to have been 
those which include the half-period of the inequality of the diurnal range, (or that 
portion of the period which is comprised between the epochs of minimum and maxi- 
mum,) are precisely the same years over which my discussion of the disturbances 
has extended, and from which I have been led to infer the probable existence of a 
periodical inequality in those phenomena also, having the very same epochs of mini- 
mum and maximum. Dr. Lamont confines himself entirely to the diurnal inequality 
of the Declination, leaving untouched the subject of the disturbances (or, as they are 
more usually termed in Germany, the magnetic storms). 
Whether the progressive increase so distinctly marked in the two classes of phe- 
nomena between the years 1843 and 1848 be or be not the result of causes which 
have a periodical action, in a cycle which may be either of regular or of variable 
duration, the fact of the progressive increase being concurrent in both classes is of 
no slight importance. It tends to indicate a causal connection subsisting between 
the disturbances and the diurnal variation ; which latter, in addition to the laws 
which point directly or indirectly to the sun as the origin of its every-day phenomena, 
has other phases which mark unmistakeably, and at stations very variously situated 
in geographical and magnetical respects, the equinoxes as epochs of periodical change. 
The investigation, of which the results are contained in this paper, has shown that the 
disturbances have also a law of diurnal action, depending like that of the regular 
