92 Physical Discovery. 



This discovery, is not a mere speculation, — a simple project, but 

 it is an invention that has been tested by experiments, which the au- 

 thor has actually made. We have had the satisfaction of seeing them 

 made in our presence ; and we, moreover, have in our cabinet, the 

 first compass of this kind, which the author has constructed and con- 

 fided to us. The explanation which he has given us, of his magnetic 

 process, is equally curious, and satifactory. 



The little needle, according to his theory, endeavors as much as it 

 is enabled, and on its own account, to approach the north like all other 

 magnetic needles, to within about twenty degrees. It is counteracted 

 in this direction, by the large needle, which, of right, preoccupies that 

 position, and takes possession of it ; but as the effort of the small nee- 

 dle cannot be inconsequential, its rival, finds itself to be pushed a lit- 

 tle farther, this impulsion acting by reason of the quantity of inherent 

 power in the little needle. 



The author cencludes that the deviation which is observable in the 

 common compass, results from an actual defect in the magnet, that 

 is, from a weakness in its directing power ; and that it is from this de- 

 fect in its power, that the common magnetic needle does not now 

 point to the true north, as it did in 1666, whereas by associating with 

 it, another needle, it is rendered, by this auxiliary combination, that 

 nineteen twentieths degree of power which it wants at the present 

 time to attain this object. 



Such a discovery as this cannot but excite the curiosity of all the 

 friends of the arts ; and we consider it as calculated to extend the 

 sphere of acquired knowledge, on the character and properties of the 

 magnet, a complete union of which, according to some philosophers, 

 should result in a theory of longitude. At all events, we can, with 

 reason, flatter ourselves, (thanks to the invention which we have made 

 public,) that the mariner's compass, is advancing towards perfection. 

 In fact, the common magnetic needle has only one cause of direction, 

 which is deranged by the least extraneous impulse, whereas the new 

 needle, combined, as has been described, tends to a point, where it 

 is fixed by two directive causes, which form an angle, and by which 

 it is, in a manner, confined, which necessarily, renders it less unsta- 

 ble, less capricious, and less subject to variation. 



