and Intensi of the Magnetic Needle. 351 



In a few instances the maximum deflection of the needle to the 

 westward occurred as early as 8^ a. m., and as late as 3^ p. m. ; and, 

 in the like manner, the greatest deflection eastward took place at 2^ 

 and 3^ p. m., on some few occasions. In all these anomalous cases, 

 however, it was remarked, from simultaneous observations on the 

 times of vibration of a suspended horizontal needle, that these irre- 

 gularities were evidently due to an extraordinary alteration in its 

 intensity, which produced a deflection contrary to the regular order 

 of the motion of the needle. 



The diurnal change of direction appears, by these observations, 

 to have been seldom less than one degree, and sometimes to have 

 amounted to five, six, and even seven degrees j and there can be no 

 doubt, that the changes in this amount were more or less due to the 

 position or influence of the sun, and probably of the moon, on the 

 terrestrial magnetic sphere ; but the particular law of this influence 

 is a question of great delicacy, and of intricate research, and will be 

 best left to the investigations of those who are theoretically conver- 

 sant with these subjects. 



After these general observations, the tables to which they allude 

 follow ; these, however, occupy forty quarto pages, and, of course, 

 we can only attempt a general explanation of them j they are given 

 under the follow mg title. 



" Tables, shewing the observed daily variations of the horizontal 

 needle, from 10th December to 31st December 1824 ; and from 1st 

 January to 31st May 1825, at Port Bowen. Lat. 73° 14' N., long. 

 88° 54' W. Mean dip 88° 1'.4 N., and mean variation 124°''W." 



After 1st January, when the general series commenced, these ta- 

 bles exhibit the deflection of the two needles No. 1. and No. 2. for 

 every hour, and frequently intermediate observations, to the end of 

 the series, with the registered temperature at the moment of obser- 

 vation ; but, as I have already observed, they are too extensive to al- 

 low us to attempt a regular detail of them. 



Lieutenant Foster has, however, in a subsequent article, given a 

 general abstract of the five months' observations, and this, by a lit- 

 tle farther abridgment, will reduce them to such a compass, as to 

 allow of their being inserted in the pages of the Journal. Here we 

 have given only the greatest amount of the daily variations for every 

 day, and the hours and minute when the needle had its greatest and 

 least westerly bearing ', or the time of maximum westerly and eas- 

 terly variations ; the temperature at those times ; the state of the 

 winds and weather, with a column, also indicating whether the au- 

 rorae boreales were, or were not, visible. These tables will be suffi- 

 ciently intelligible, with one remark, namely, that, in the column 

 marked A, M., the hours sometimes exceed twelve, and ought, there- 

 fore, to have fallen in a column marked P. M. ; but, to save room, 

 we have preferred the above notation, which will be understood to 

 indicate the hours since midnight. The same occurs in the column 

 of maximum easterly bearings, marked P. M. Here the time indi- 

 cates the hour, &c. past noon. 



