CHKISTCHURCH TERM-DAY OBSERVATIONS. 203 



Referring to the hourly values of this element given on p. 179 of the " Physical Observations," it will be 

 noticed that a considerable number of discontanmtiefl presented themselves, while the <lail\- rank's were 

 exceedingly small. The former phenomenon throws some doubt on the smooth working of the instrument, 

 and the latter indicates that, even if the data were as trustworthy aa those for the other two elements, 

 they would form a less promising field of investigation. 



The choice between Declination and Horizontal Force was more dillicult. The examination, however, 

 of the results from the few representative days pointed to the conclusion fully confirmed by subsequent 

 investigation that the diurnal variation of Declination is decidedly more regular at Christchurch than 

 that of Horizontal Force, and, accordingly, that it is the latter element whose changes promise the greatest 

 return to minute examination. Accordingly, I recommended that publication of complete details of the 

 variation throughout the whole duration of term days should be confined to Horizontal Force (pp. 204-228), 

 and that in the case of the Declination (pp. 229-230) full details should be given only for the term hours. 

 The Vertical-Force changes are not individually shown at all. Though details of the variations of 

 Declination and Vertical Force are published only partially, or not at all, these variations were carefully 

 studied and tabulated and a number of conclusions have been deduced. 



D 2 



