24i'l> M. Kreil's Magnetic Observations, 



The minimum of inclination was at 8 a.m. in the winter 

 months (i. e. November to March) and at 11 p.m. in the re- 

 maining months, with the exception of June and July, when 

 it took place as early as 7. 30' p.m. 



These results are deduced from the general or monthly 

 means of the different hours of observation. Another com- 

 bination of the observations in daily means, i.e. the averages 

 of all the observations taken on the same day, ought to show 

 those alterations which have a period longer than a day and 

 less than a year: a monthly period is thus shown; but as yet 

 it is only in the horizontal elements that it can be recognised 

 with certainty. The observations with the inclinatoriiim have 

 not been brought into the calculation, because they were 

 frequently interrupted, and because at first the axis of oscilla- 

 tion of the needle was too far removed from its centre of 

 gravity. 



12. If the daily means of the times of vibration of the 

 horizontal needle reduced to the temperature of 0, are com- 

 bined together in such series that the middle of each shall 

 coincide with a phase of the moon, and if the means of these 

 series are freed from the influence of the loss of magnetism 



CD 



of the needle by being reduced to the same epoch, we then 

 see that the total means of all the times of vibration observed 

 near the new moon, and during the first quarter, are less than 

 those near the full moon and in the last quarter. If we 

 compare the different months with each other, we see that 

 the phasnomenon, as it is here enounced, is only found in the 

 eight months from November to June, and that in the four 

 remaining months, i. e. July to October, the contrary takes 

 place; for in the latter interval the longest times of vibration 

 coincide with the new moon and the first quarter, and the 

 shortest times of vibration with the two other phases. 



13. This phoenomenon might be thought to be an effect of 

 the rotation of the sun round its own axis, which, supposing 

 the sun to be magnetic, would cause sometimes one and some- 

 times the other of the poles of its magnetic axis to be turned 

 towards the earth ; and this hypothesis would also explain 

 the alternations of the phffinomena according to the different 

 seasons of the year, as the earth is opposite to one or the 

 other of the solar hemispheres according as she is in the 

 summer or in the winter half of her orbit : but this will not 

 hold good. The epoch of the least value of the intensity is 

 open to the objection that the time of rotation of the sun is 

 two days shorter than the time of the synodic moon, and this 

 difference of time combined with the different positions of the 

 earth relatively to the sun, would cause the phasnomenon to 



