ON MAGNETIC DISTURBANCES AT TORONTO. 163 
turbances of all the elements in the year ending 30th June, 1854. The 
observations during that year were taken under rather unfavorable 
circumstances. Portions of the building were in the course of recon- 
struction, and workmen with iron tools were much about the premises, 
but as I have been informed that great care was always taken to ascer- 
tain that no iron was left in dangerous proxmity to the instruments 
during the observations, I cannot ascribe wholly to this cause, the 
anomalous character of the results. It will be seen, that of the three 
instrumentally independent elements, the vertical force was most affect- 
ed, the aggregate in this year of expected minimum actually exceeding 
that of 1848, the epoch of maximum. 
One clue towards the solution of this difficulty may be sought from 
an examination of the relative magnitudes of the annual mean ranges 
of the regular diurnal variations of declination, which, according to past 
experience, correspond very generally with the annual aggregates of 
disturbance. Taking the amplitudes or ranges, as the angle between 
the mean positions of the needle, at 8 a. m. and 2 p. m., we have 
| 
YEARS, sais | 1846|1847|1848 1862 
so-so 10751 859 
| 
1860 | 1861 
* Amplitudes of diurnal 
variation of Declination.|7.96/8.60/8.64/8.64 1066 9.03 |8.00/8.30/9.69/11.40 
12.3411.92)10.65 
It will be here noticed, that although the range in 1853-54 is larger 
than those of 1844, ’45, °46, °47,’56, °57, the preponderance is not 
such as to warrant any decided inference in explanation of the anomaly 
in question. It is possible that the disturbance period, which, during 
the few years that have been examined, has approximately coincided 
with the decennial period in the appearance of solar spots, may, im 
addition to the cause thus suggested, be due to some other variable 
and less powerful influence, the length of whose period may be nearly 
equal to or nearly a multiple of ten years. Should such an influence 
exist, the approximate but not accurate superposition of the maxima of 
the two periods in some cycles, and their interference and antagonism, 
in others, together with perhaps /ocal causes, would account both for 
the general correspondence and the occasional anomalies. 
* The effects of disturbances are not eliminated from the amplitudes from 1848 to 1860. To 
render them comparable with those of the subsequent year they should be each increased 
by about 0'.43. 
