THE BEARINGS OF MAGNETIC OBSERVATIONS. 91 



that "the kingdom can be divided into magnetic districts 

 in which the relations between the direction of the disturb- 

 ing forces and the main geological characteristics are so 

 suggestive as to be worthy of careful statement and further 

 investigation," not only holds good, but has received con- 

 firmation. 



The mining engineer is deeply interested in a know- 

 ledge of the Declination. Charts of normal lines are of 

 great use to him whether above or below the earth's surface, 

 but especially below when he has no other guide. To such 

 an one a knowledge of regional magnetic disturbance as de- 

 duced from surface observations is most important, as it 

 tells him that he is in the neighbourhood of magnetic 

 rocks, the disturbing effect of which on his compass needle 

 may be far greater in the depths of his mine and turning it 

 into a treacherous guide. 



We have now considered magnetic observations in a 

 measure from the point of view of the immediate practical 

 results which their scientific treatment produces, but who 

 will say in this great maritime nation that the work of mag- 

 netic observers, even if solely to make navigation poss'ble, 

 is not worthy of the fullest consideration ? 



There is besides a vast field of inquiry for the observer of 

 terrestrial magnetism in unravelling thesecretsof the earth con- 

 sidered as a magnet, and the ceaseless change of its magnetic 

 condition which the needle tells us of, for which no immediate 

 practical result can be foreseen, yet is worthy of the attention 

 of the ablest physicists and most advanced mathematicians. 



Inquiry into the causes of the secular change is one 

 requiring the fullest attention, but observation has not yet 

 done sufficient work. It certainly has done much in certain 

 countries, and for a large portion of the world as regards 

 secular change in the past, and data obtained for predicting 

 future changes for a few years, but only one expedition has 

 examined the Antarctic regions magnetically, and it is 

 doubtful if any substantial progress will be made until a 

 second expedition is made thither, one profiting by the 

 experience of its precursor, and equipped with possibilities 

 for work hardly hoped for by Ross. 



