MATTER 265 



There is another possibility to which I can only briefly 

 refer here — namely, that the ether is to be conceived as a 

 perfect fluid, but that just as a certain type of motion of 

 this ether corresponds to the atom, so types of motion 

 may be used to stiffen the ether, or to give it elastic 

 rigidity. The ether may be a perfect fluid, but, owing to 

 the turbulence of its motion, it may act for certain pur- 

 poses as a perfect jelly. This hypothesis will be better 

 appreciated when I have said a few words as to the ether- 

 motions which may constitute the prime-atom. 



§ 10. — TJie Vortex-Ring Atom and the Ether-Squirt Atom 



In constructing an atom out of an ether-motion we 

 have first to gain some idea of how it is possible that 

 ether, not being itself hard or resisting change of shape, 

 can yet be conceived to produce the sensations of hard- 

 ness and resistance by its motion. Some general idea 

 can easily be got of the sort of resistance produced by 

 particular types of motion in the following manner : Take 

 an ordinary spinning -top, and suppose we succeed by 

 great care in balancing it on its peg. Clearly the least 

 touch of the hand will upset it ; it offers no resistance to 

 the motion of the hand. The same remark applies if the 

 peg of the top were fixed by a ball-and-socket joint to 

 the table. But, on the other hand, if the top be set 

 spinning, we shall find the case entirely altered ; it will 

 now present considerable resistance to being upset, and, if 

 partially turned round its ball-and-socket joint, will tend 

 to return to the old vertical position. A considerable 

 number of such spinning-tops would offer a large amount 

 of resistance to a hand passed over the table at a less dis- 

 tance than their height. This example may perhaps bring 

 home to the reader how a certain type of motion may suffice 

 to stiffen a body not otherwise stiff. Another example 

 of motion stiffening a body is the smoke-ring, with which 

 most devotees of tobacco are well acquainted. Two such 

 smoke- rings will not coalesce ; they pass through or 

 wriggle round each other, and round solid corners which 



