362 
COLONEL SABINE ON PERIODICAL LAWS DISCOVERABLE 
depending upon the relative circumstanees of the sun, and the earth and her satel- 
lite. The cycle might or might not be one of regular and unfailing recurrence. 
The observational evidence to which we are indebted for a knowledge of its exist- 
ence, though sufficiently decisive as far as the period of observation extended, could 
only be viewed, in reference to a permanently cyclical character of the phenomenon, 
as fragmentary, and as the commencement of an investigation which would require 
to be pursued in one or more of the permanent magnetic observatories established in 
our own and other countries. Had no other circumstance presented itself to give an 
additional interest to an investigation which thus held out a fair promise at least of 
making known laws of definite order and sequence in phenomena vdiich have excited 
so much attention of late years, but of which so little is even yet known; — had for 
example the decennial j)eriod, which appeared to prevail with precisely corresponding 
features in two distinct classes of the magnetic variations, connected itself with no 
other periodical variation either of a terrestrial or cosmical nature with which we are 
acquainted, — there might have been indeed little reason to apprehend that the inves- 
tigation would have been suffered to drop : but the interest and importance of the 
inquiry have doubtless been greatly enhanced by the remarkable coincidence, which 
it was the object of the paper communicated to the Royal Society in March 1852 to 
announce, between the above-described periodical inequality by which the magnetic 
variations referable to solar influence are affected, and the periodical inequality which 
has been discovered by M. Schwabe to exist in the frequency and magnitude of the 
solar spots. The coincidence, as far as we are yet able to discover, is absolute ; the 
duration of the period is the same, and the epochs of maximum and minimum fall in 
both cases in the same years. The regularity with which the alternations of increase 
and decrease have been traced by M. Schwabe in his observations of the solar spots, 
which have been now continued for about thirty years, must be regarded as conferring 
a very high degree of probability on the systematic character of causes, which are as 
yet known to us only by the visible appearances which they produce on the sun’s disk, 
and by the disturbances which they occasion in the magnetic direction and force at 
the surface of our globe. As a discovery which pi omises to raise terrestrial mag- 
netism to the dignity of a cosmical science, we may feel confident, that, although the 
Colonial Observatories have been brought to a close, the investigations which they 
have thus successfully commenced will be pursued to their proper accomplishment, 
in those national establishments which have a permanency suitable for such under- 
takings. 
The conclusions which have been drawn, both in the Philosophical Transactions, 
and in the introductory discussions in the Toronto and Hobarton volumes, regarding 
the periodical laws of the disturbances at those stations, have been hitherto confined 
exclusively to the disturbances of a single element, the Declination. It was fully 
recognized that each of the other two observational elements, viz. the Horizontal and 
he Vertical Forces, might be expected to furnish concurrent but strictly independent 
