BEYOND THE LIMITS OF VISION. 17 



cloth send out through the opposite hole ring after ring of the 

 smoke, chasing arid passing through each other, bounding and 

 vibrating as they come into contact. These are what are called 

 vortex rings, little whirlpools in the air. The particles of the 

 smoke are rapidly revolving in the perimeter of the ring, and a 

 constant current of air is passing through the center. You would 

 feel this little blast of air quite sensibly if you placed your cheek 

 in the way of one of these vortex rings. 



Ilelmholtz has shown by mathematical demonstration that if 

 the air were a perfect fluid, that is if it flowed in all its parts 

 absolutely without friction, those rings once started would go on 

 rolling forever, and no power could destroy them, for they 

 instantly bound away from every thing that would touch them. 



Furthermore, Helmholtz has shown that in such a fluid the 

 form of the rings need not necessarily be circles, but may be 

 figure eights, or any other continuous and knotted folds. And 

 the form impressed on them at their birth will continue to be 

 their form as long as matter lasts. 



Now this is the essence of that bold conception which I told 

 you about concerning the constitution of the ultimate atoms 

 which go to make up our world. Minute portions of the infinite- 

 ly fine and subtle matter of universal space are in some way set 

 to whirling in innumerable little eddies and in certain stable 

 forms, which by the incessant beating of the etherial particles, are 

 compelled to approach each other, yet when they strike, their own 

 vortex motion makes them rebound and react on each other in 

 the manner constituting molecular motion. 



I cannot tell you how the atoms were first started in this 

 vortical whirl ; nor why they are of certain constant patterns, 

 and in a certain limited number of forms. Nor can I tell why 

 they join together so capriciously to form the various substances 

 which surround us. But this I know, that when once the atoms 

 have been cast in their tiny moulds and emptied into space in the 

 quantity and with the affinities they have, it is not a difficult 

 thing to build a world out of them, nor to account for the laws 

 which will govern it. 



