THE STORY OF NINETEENTH-CENTURY SCIENCE 



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 inde- 

 structible vortices. And at once Lord Kelvin bethought 

 him of the frictionless medium which physicists had now 

 begun to accept the all-pervading ether. What if vor- 

 tex rings were started in this ether, must they not have 

 the properties which the vortex rings in air had exhib- 

 ited 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 plausible 

 conception of the constitution of matter hitherto formu- 

 lated. It is only a theory, to be sure ; its author would 

 be the last person to claim finality for it. "It is only a 

 dream," Lord Kelvin said to me, in referring to it not long 

 ago. But it has a basis in mathematical calculation and 

 in analogical experiment such as no other theory of mat- 

 ter can lay claim to, and it has a unifying or monistic 

 tendency that makes it, for the philosophical mind, little 

 less than fascinating. True or false, it is the definitive 

 theory of matter of the nineteenth century. 



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