IN THE MEAN EFFECTS OF THE LARGER MAGNETIC DISTURBANCES. 115 
in the three first years are, at Toronto 0’69, and at Hobarton 0-68 ; whilst in the 
three last years they are at Toronto T33, and at Hobarton T34. Facts of such 
remarkable character, evidenced by the independent and concurrent testitnony of so 
large a body of observations at stations so widely distant from each other, seem 
to be well deserving the consideration of magnetical physicists ; more particularly 
of those who are disposed to regard thermometrical differences as the cause of the 
periodical and other magnetic variations. The ratios of disturbance in the years 
1846, 1847 and 1848, were nearly twice as great as in the years 1843, 1844 and 
1845. Did there occur any notable differences of either local or general temperature, 
or thermometrical peculiarities of any description, in the years in question, to which 
variations of such magnitude in the ratios of magnetic disturbance can be ascribed, 
or with which they can be connected ? 
We should not however derive all the advantage which an examination of the 
ratios in Table XIII. seems suited to afford to those who desire to obtain an insight 
into the character of the variations they represent, were we to overlook the still 
more remarkable fact which they manifest, of a general, and with a single exception, 
uninterrupted progressive increase in the amount of disturbance from a minimum 
in 1843 to a maximum in 1848. 
The interruption is in 1845, when the ratios, both of numbers and values, are less 
than in 1844. This interruption of the perfect continuity of the progression occurs 
alike at both stations ; it is not of large amount, and is the sole exception to an 
otherwise continuous increase in the amount of disturbance during the years com- 
prehended in this investigation. 
The accordance with which the ratios at Toronto and Hobarton indicate this pro- 
gression, is scarcely less remarkable than are the facts which they combine to indi- 
cate. It is indeed difficult to regard results so strikingly correspondent in any other 
light, than as independent and mutually corroborative measures of the same general 
phenomenon ; and to view the inconsiderable differences between the ratios of the 
several years at the two stations as due either to accidents of observation, or to the 
want of strict simultaneity in all cases which has already been described. In such 
case a combination of the ratios obtained in opposite hemispheres would perhaps 
present a not improbable approximate view of the general variation in the amount 
of disturbance in the different years, occasioned in both hemispheres by the class 
of phenomena under notice. It is contained in the following Table. 
Table XIV. — Mean of the ratios at Toronto and Flobarton. 
Years. 
Numbers. 
Values. 
1843 
0-60 
0*52 
1844 
0-78 
0-78 
1845 
0-72 
0-65 
1846 
1-20 
M5 
1847 
1*28 
1-42 
1848 
1-43 
1-31 
Q 2 
