and Intensity of' the Magnetic Needle. 365 



to complete a comparison he has so happily begun, by being al- 

 lowed to pursue his experiments in the southern hemisphere. 



If, as has been said, all knowledge is valuable, that must be 

 more especially so which contributes to the comforts, necessities, 

 and preservation of human existence ; and that a correct know- 

 ledge of the theory of terrestrial magnetism is entitled to rank 

 in this class, cannot be doubted, when we reflect, that it would 

 enable us to add to the facilities of commerce, to the security of 

 navigation, and tend materially to the preservation from ship- 

 wreck and death, of those brave men to whom England is so 

 much indebted for her pre-eminence amongst nations. 



It is a subject, however, which cannot be pursued with ad- 

 vantage in the closet ; at least the data must be drawn from ac- 

 curate observations made in various and remote situations on 

 the globe, which can only be obtained through the assistance 

 and support of governments,— and no government can be so 

 much interested in the inquiry, as that which directs the ef- 

 forts of a nation, whose pride and^boast is to be the first mari» 

 time power on the globe. The British Admiralty, then, is the 

 rock on which -we build our hope for a more complete know- 

 ledge of the law s of terrestrial magnetism ; and, after the libe- 

 ral support it has already given to these inquiries, we feel con- 

 fident that our hope is not ill founded. 



At some future time I propose to examine the magnetic ex- 

 periments of Captain Sabine, and endeavour to show, that 

 the theory in question will also serve to explain the anoma- 

 lies he found in the deep intensity of the needle in the torid 

 and temperate zones, and which led him to look for a pole of 

 intensity distinct from that of direction, — not reflecting that the 

 formula he employed was rendered Inapplicable the moment he 

 assumed the separation. 



