Sect. III.] Mai^uc/ism. T; 



have been more satisfactoriiy ascertained ; and a 

 nearer approach made than Ibrmerly to a systema- 

 tic arrangement of the magnetic laws. 



The unexpected and daring introduction of ma- 

 thematical principles and demonstration into tin; 

 dark regions of electriciijj, by Mr. /l^pinus, was 

 mentioned, in a former page, as one of the signal 

 improvements of the last century, lliis ingeniouji 

 philosopher has done the same in viagnctistn^ and 

 with equal success^. And though this subjection 

 of the magnetic principles to the most precise and 

 definite of all species of investigation does not ap- 

 pear to have led, as yet, to any extraordinary dis- 

 coveries, or radical reforms in tbeory ; yet it has 

 been by no means without its use, and may con- 

 duct to invaluable acquisitions f. 



The Mariner's Compass, within the period in 

 question, has been considerably imjjroved. Tliis 

 important instrument, after its invention in ISOL^ 

 long remained in a rude and imperfect state. But 

 Dr. Knight's discovery of the mode of making ar- 

 tificial magnets, about the year 1744, together 

 with the results of some other experiments, en- 

 abled him to render the compass much more con- 

 venient and useful J. To his improvements may be 

 added the further emendations of Mr. Smeaton and 

 Mr. M'Culloch, both of Great Britain. 



The variation of the magnetic needle has been a 

 subject of much attention and of much ingenious 

 speculation, during the past century. The obser- 



* Tvntamcn Thcorict Magn. ct Elect r. Pclrop. 1750. 

 t See Additional Notes — (1). 

 1 S(^c Additiomil Notes — f/vj. 



