362 Mr. Tomlinsoris Experiments and [May 



and then removed, and the ear be applied close to the 

 glass, the note will be distinctly heard to consist of such 

 sounds as 



woo, woo, woo, woo, icoo, 

 and so on until all vibration ceases. 



13. In my early attempts to ascertain the nodes by means 

 of wire, I observed a very curious effect : I had employed 

 a piece of iron wire, entirely free from magnetism, placed 

 one end at the bottom of the glass, and the other resting 

 against the »side. On vibrating the glass containing the 

 wire, I found that it invariably turned towards the north, 

 and continued to vibrate there in the plane of one magnetic 

 meridian. I employed copper and brass wire, always with- 

 out the same effect. I therefore assured myself of the cor- 

 rectness of the first experiment, and got two or three friends 

 to repeat it, but the result was undoubted. I even found 

 that the result was obtained when the glass was half filled 

 with water or oil, so as to cover the wire, and that the 

 motion of the wire, and its retention towards the north, 

 seemed facilitated by that fluid. 



14. In explaining this experiment I must refer to the 

 mode of inducing magnetism by percussion, such as an 

 inclined poker or bar of iron when struck by a hammer. 

 The blows strongly vibrate every particle of the mass of 

 metal, and, by a process not clearly comprehended, mag- 

 netism is induced. Now, in the above experiment, vibra- 

 tion, by a somewhat analogous process, renders the wire 

 slightly magnetic, and being free to move, it is of course 

 attracted by the magnetic force. 



15. To return, however, to the vibrating mercury, we 

 must consider that as the vibrating parts of the glass act at 

 right angles to the mercury, the edge of that fluid is, as it 

 were, attracted and repelled, and the the first band of 

 undulae moves in the direction of the finger, as may be 

 shewn by placing a small shot or other small body on the 

 mercury, leaning from its convex edge against the side of 

 the glass. The attractions and repulsions that I speak of 

 may be illustrated by surrounding the mercury with a circle 

 of small shot at the circumference. If the glass be then 

 vibrated the shot becomes agitated in a singular manner. 

 All seem actuated by a uniform vibrating motion, and the 



