THE JOURNEYING ATOMS 



fied; but in a chemical combination, say like iron 

 sulphide, no amount of magnification could reveal 

 the two elements of iron and sulphur. They no 

 longer exist. A third substance unlike either has 

 taken their place. 



We extract aluminum from clay, but no conceiv- 

 able power of vision could reveal to us that metal in 

 the clay. It is there only potentially. In a chemical 

 combination the different substances interpenetrate 

 and are lost in one another: they are not mechani- 

 cally separable nor individually distinguishable. 

 The iron in the red corpuscles of the blood is not 

 the metal we know, but one of its many chemical 

 disguises. Indeed it seems as if what we call the 

 ultimate particles of matter did not belong to the 

 visible order and hence were incapable of magni- 

 fication. 



That mysterious force, chemical affinity, is the 

 true and original magic. That two substance* 

 should cleave to each other and absorb each othei 

 and produce a third totally unlike either is one or 

 the profound mysteries of science. Of the nature of 

 the change that takes place, I say, we can form no 

 image. Chemical force is selective; it is not promis- 

 cuous and indiscriminate like gravity, but specific 

 and individual. Nearly all the elements have their 

 preferences and they will choose no other. Oxygen 

 comes the nearest to being a free lover among the 

 elements, but its power of choice is limited. 



195 



