12G 
LIEUT.-COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
are very nearly in the same latitude, but in different hemispheres as respects the equator, 
and are both extra-tropical ; they also differ about fifteen hours of longitude from 
each other. Simultaneous observations occurring in the winter months of the one 
station fall therefore into the summer months of the other ; and the day observations 
of the one are for the most part the night observations of the other. The clocks which 
gave the time for the observations were regulated at both stations to show the mean 
solar time of the meridian of Gottingen, O'* 15"^ west of Hobarton, and 55“ east 
of Toronto. The observations were made at the completion of every hour of mean 
solar time at Gottingen. By this pre-arrangement the whole body of observations 
during the three years would have been synchronous in respect to absolute time, but 
for the circumstance that no observations were made on the Sundays, the Christmas 
days and the Good Fridays ; all which days being regulated, agreeably to the pur- 
poses for which they were excepted, by local time, it followed that in consequence of 
the difference of meridians between the two stations, there were fifteen observations 
in each of fifty-four days of each year at each station which had no corresponding 
observations at the other station. The proportion of these to the whole body of ob- 
servations is about one-ninth ; consequently about eight-ninths of the whole were as 
strictly synchronous as such observations can conveniently be made. As it is not 
the object of this paper to examine the precise degree in which the so-called irregular 
disturbances are synchronous in different parts of the globe, I do not permit myself 
to enter into details on this part of the general subject, reserving such details for a 
more appropriate occasion ; I will merely state generally that the evidence of the 
synchronous character of the disturbances afforded by the observations of these three 
years is not less remarkable than has been stated on other occasions ; and I will pro- 
ceed at onee to their distribution into the months and hours of their respective oc- 
currence, first at Toronto and then at Hobarton, and to the evidenee afforded thereby 
of the periodical influence by which their mean effects appear to be governed. 
The disturbances to be examined are those which, occurring only occasionally, and 
apparently irregularly, are indicated by the wide departure of the magnetic instru- 
ments from their mean or normal positions at the same hours and at the same period 
of the year. It is no doubt probable that the causes in which they originate do also 
produce smaller disturbances of the same class and apparently irregular occurrence ; 
but no characteristics have yet been established by which the'smaller disturbances of 
this class may be distinguished from irregularities in the action of causes of known 
periodical character and regular occurrence. That such characteristics may exist and 
may hereafter be recognized, so as to beeome the subjects of observation and a means 
of effecting a complete separation between the two classes of phenomena, is also pro- 
bable ; but it is not necessary to wait till then in order to assure ourselves that the 
larger disturbances, viz. those which may be separated from the others by their mag- 
nitude alone, are, notwithstanding their seeming irregularity, subject in their mean 
values to periodic laws, which are quite distinct from those of any class of disturb- 
