516 EDITOR'S NOTES. 



residual diurnal variation is virtually a single progression 

 with but one maximum and one minimum. 



The belief that the " nocturnal episode " is, in great 

 part, at least, if not wholly, the effect of the disturbances, 

 is further strengthened by the analogous facts of the 

 diurnal variation of the total magnetic force at Toronto, 

 discussed in pp. xciii xcv of the same volume. When 

 the diurnal variation of this element is obtained from 

 the whole of the observations, including the disturb- 

 ances, two well marked maxima and minima appear in 

 the twenty-four hours ; but by eliminating the disturb- 

 ances in a greater or less degree, by a process similar to 

 that adopted in the declination, one of the two maxima 

 and one of the two minima diminish in proportion to 

 the degree in which the disturbances are removed, 

 giving full reason to believe that by eliminating their 

 influence altogether, the residual diurnal variation would 

 be reduced to the simple form of a single progression in 

 twenty-four hours. 



There is also reason to believe that the supposed ano- 

 malies in the turning hours of the diurnal-variation which 

 have been observed in the high latitudes, and which are 

 adverted to in pages 129 and 130 of this volume, are pro- 

 duced by the disturbances. At the only station in the 

 high latitudes where the large disturbances have been se- 

 parated, viz. Point Barrow (Phil. Trans. 1857, Art xxiv.), 

 the effect of the separation has been to remove the mask 

 by which the true features of fche solar-diurnal variation 

 were concealed, and to restore its turning hours 

 accordance with the order of the phenomena observ 

 generally in the same hemisphere. 



: 

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