A HISTORY OF SCIENCE 



tinned its course as if nothing had happened. When, 

 on the other hand, two rings moving in slightly differ- 

 ent directions came near each other, they seemed to 

 have an attraction for each other ; yet if they impinged, 

 they bounded away, quivering like elastic solids. If 

 an effort were made to grasp or to cut one of these rings, 

 the subtle thing shrank from the contact, and slipped 

 away as if it were alive. 



And all the while the body which thus conducted 

 itself consisted simply of a whirl in the air, made visi- 

 ble, but not otherwise influenced, by smoky fumes. 

 Presently the friction of the surrounding air wore the 

 ring away, and it faded into the general atmosphere 

 often, however, not until it had persisted for many sec- 

 onds, and passed clear across a large room. Clearly, if 

 there were no friction, the ring's inertia must make it a 

 permanent structure. Only the frictionless medium 

 was lacking to fulfil all the conditions of Helmholtz's 

 indestructible vortices. And at once Lord Kelvin be- 

 thought him of the frictionless medium which physi- 

 cists had now begun to accept the all-pervading ether. 

 What if vortex rings were started in this ether, must 

 they not- have the properties which the vortex rings 

 in air had exhibited inertia, attraction, elasticity? 

 And are not these the properties of ordinary tangible 

 matter? Is it not probable, then, that what we call 

 matter consists merely of aggregations of infinitesimal 

 vortex rings in the ether ? 



Thus the vortex theory of atoms took form in Lord 

 Kelvin's mind, and its expression gave the world what 

 many philosophers of our time regard as the most 

 plausible conception of the constitution of matter 



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