404 



cient for present theoretical purposes, the character and amount for 

 each element of the regular daily effect of the moon on the terrestrial 

 magnetic phenomena, the existence of which does not appear to have 

 been even suspected at the time when the Report of the Committee 

 of Physics was drawn up. The discovery of the moon's influence on 

 any of the magnetic elements is due, as already stated, to M. Kreil ; 

 but Toronto is the first, and as yet the only, station, at which the 

 numerical values at every lunar hour of the lunar- diurnal variations 

 of the three elements have been published. Corresponding state- 

 ments to that which has been given for Toronto, will be found for 

 St. Helena and Hobarton, in the volumes of those observatories, 

 which are now in preparation. All the results at the three stations 

 present the same general characters. The lunar influence does not 

 appear to participate in the decennial inequality which is found in 

 all the solar variations (Phil. Trans. 1857, Art. I.). The lunar- 

 diurnal variation of each of the elements is a double progression in 

 the twenty-four hours, having epochs of maximum and minimum 

 symmetrically disposed. In character, therefore, it differs from 

 what might be expected to take place if the moon were possessed of 

 inherent magnetism, i. e. if she were a magnet, as it is usually 

 termed, per se ; and accords with the phenomena which might be 

 expected to follow if she were magnetic only by induction from the 

 earth. On the other hand, it is believed that the amount of the 

 variation, as observed at each of these stations, very far exceeds what 

 can be imagined to proceed from the earth's inductive action re- 

 flected from the moon. In this theoretical difficulty we are naturally 

 thrown back to seek a more extensive knowledge of the phenomena 

 than we have yet obtained, and to the generalization which will follow, 

 when sufficient materials for it have been procured. In subordinate 

 particulars, a difference, which is apparently systematic, is perceived 

 to exist in regard to the hours which constitute the epochs of maxima 

 and minima at the three stations, as well as in regard to the amounts 

 of the respective variations ; these differences are no doubt intimately 

 connected with the causes of the phenomena, and are likely to lead 

 to their elucidation. It is therefore greatly to be desired that the 

 number of stations furnishing complete determinations, such as the 

 Colonial Observatories only have hitherto supplied, should be in- 

 creased. 



