ON EAPID STREAMS. 101 



meeting of the opposite forces will be similar to 

 that produced by striking sharply a globe of 

 glass, or of compact uniformly dense metal at any 

 point, when the fracture of the globe will be found 

 at a spot diametrically opposite to the point of 

 concussion where, indeed, the vibrations tra- 

 versing in radii from the point struck will im- 

 pinge on one another ; here, then, will the force 

 have so accumulated that the molecular disturb- 

 ance of matter will be sufficient to separate its 

 particles, and so cause a fracture of the globe. It 

 seems to me, that this just explains the fracture 

 of these rods, weak in the back, so to speak, 

 causing an interruption of action or, as I have 

 called it, a double action, when fracture so fre- 

 quently follows sharp striking or even violent 

 movements with a heavy line in windy weather, 

 when forces exerted at the opposite ends of the 

 rod will surely cause fracture of the rod at this 

 point of meeting or concurring vibrations. It is 

 .true, that by pulling violently at either end of a 

 rod with a sudden jerk, it will snap in its weakest 

 point, as any common stick will snap when bent 

 between the hands, but it is not thus that rods 

 are commonly broken ; it is not by the immediate 

 direct force applied, but by waves of vibrations 

 transmitted along the rod increasing and multi- 

 plying in their power during their progress, that 

 the unfortunate disaster occurs if the former 

 were the common cause, we need not have so 

 long considered the subject ; it would have been 

 obvious, and its remedy easy ; but as it is by no 



