Mr Watt on the Magnetic Injiuence of the Solar Rays. 171 



free to move, it is not easily prevented from evincing the influ- 

 ence of that law which obliges it to rest parallel with the mag- 

 netic meridian ; although the intermediate body should be ap- 

 plied close to the bar, — no body interposed at any distance (if 

 not attractive) having any influence on it whatever, I found, 

 that, by coating the needle with bees-wax, or putty, the direc* 

 tive power might be variously modified ; and that, by making 

 the coating sufliciently thick, the polarity of the needle might 

 be so far counteracted, as to produce for the time a total cessa- 

 tion of its action. The magnetic bar, however, which was sus- 

 pended and balanced from the centre, gave some indications of 

 its polarity, though immersed in the midst of about a pound of 

 putty, — a proof, amongst many, of the subtilty of the magnetic 

 fluid. 



A needle traversing on a pivot is of course unfit for such 

 trials ; but when the needle is suspended horizontally by a hu-- 

 man hair, and the other end of the hair fixed to the top of a 

 glass-bell by a little wax, or suspended in any other way, it in- 

 dicates much slighter influence than in any other situation ; and 

 a human hair doubled will support nearly /^ths of a pound, a 

 horse-hair one pound avoirdupois with ease, and, if loaded, by, 

 degrees considerably more. 



I gradually increased the thickness of a layer of bees-wax 

 around the suspended needle, covering both the poles ; and I 

 perceived, that, as the thickness of the coating was augmented, 

 the north pole of the needle seemed to shew greater tendency to 

 move westward ; and, with a coating of wax of about 1 J inch di- 

 ameter, the needle pointed N. W. for several hours, and in the 

 course of ^ome days went back to N. N. W., where it remained 

 almost stationary. I repeated this experiment several times, 

 with nearly the same results. 



I also repeated the experiment with another small magnetic 

 bar of about 2 inches long, and Jth of an inch in breadth and 

 thickness, making the needle and bees-wax swim in a large ba- 

 sin of water. I incased the needle in a pound of bees-wax, 

 making it into a cylindrical shape, of half a foot long and 2| in- 

 ches in diameter. If the south pole of the bar was placed to- 

 wards the north, it turned round the pound of wax with ease ; 

 and when it became steady, it pointed several degrees more to 



