114 
COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
commencement of the next at Hobarton (18^ at Gottingen to 2^ of the following 
day), in which no observations were made at either observatory. 
In a week of seven days there are 168 hours, and deducting nine, there remain 
159 hours in each week in which observations were made at one or other of the two 
observatories, from which the ratios in Table XIII. are derived. Deducting twice 
fifteen or thirty hours from the 159, we have 129 hours in each week in which 
observations were made simultaneously at the two observatories, and thirty hours in 
which they were made at one or other observatory, but not simultaneously at both. 
A still further small deduction would require to be made from the simultaneous 
portion, on account of the Good Fridays and the Christmas days, and of the obser- 
vations accidentally missed. We may state, therefore, in round numbers, that about 
four-fifths of the whole number of observations which have contributed to form the 
ratios in Table XIII. were simultaneous at both stations, and that about one-fifth 
were not so. 
This consideration being premised, we shall be inclined perhaps to regard the 
accordance in the ratios at the two stations in different years as being quite as near as 
could be expected, even on the extreme supposition which the case will admit, 
namely, that of all disturbances being general. That they are so for the most pai't 
at Toronto and Hobarton, may be concluded from the circumstance, that by far the 
greater part of the disturbances which form the subject of discussion in this paper, 
occurred on the same days at the two stations. This may be seen by comparing the 
Tables in the Abstracts prefixed to the second volumes of the Toronto and Hobarton 
Observations, in which the 3940 largest disturbances at Toronto, and the 3469 at 
Hobarton, are placed in separate tables, showing the day and hour of the occurrence, 
together with the direction and amount of each, for the purpose of facilitating their 
intercomparison, and of aiding generally in comparisons of a similar nature between 
the observations at these.stations and the observations which by concerted arrange- 
ment may have been made simultaneously with them at other observatories. In all 
such comparisons the modifying influence of hours and periods of the year shown in 
the first and second sections of this paper, must be kept in view ; and it must also be 
remembered that the evidence of the general character of these magnetic affections, 
which may be afforded by the comparison of the observations of the Declination 
alone, may be expected to be greatly strengthened when the disturbances of the 
Inclination and of the Total Force shall have been subjected to a similar process. The 
evidence furnished by a single element must necessarily be partial and incomplete. 
Reeurring now to the ratios in Table XIII., and directing our attention to the 
character of the inequality which they show to have existed in the amount of 
disturbance in different years, the faets which present themselves most obviously 
and unquestionably to our notice are, that in the years 1843, 1844 and 1845, the 
ratios were uniformly considerahly less than iinity, and that in the years 1846, 1847 
and 1848, they were as uniformly considerahly greater than unity. The mean ratios 
