128 



The Electron Microscope 



more. Even if electron bombardment should reduce the highly 

 complex organic substances to a sort of carbon skeleton, the 

 chemist may be able to reconstruct the original, as the palaeon- 

 tologists have reconstructed extinct animals from their skeletons. 

 But there are many simpler substances, in particular the 

 metals and all the elements which, unless they are melted or vola- 

 tilized, will never be destroyed by electron bombardment, however 

 prolonged. How far can we hope to proceed in their exploration 

 by the electron microscope? In particular, can we expect to see 

 single atoms, and to what detail ? Let us for the moment abstract 

 from the spherical aberration. However great the difficulties in 

 the way of reducing it, they are of a technical order. But there 

 are other limitations of a more absolute nature, inherent in the 

 exploring agent, the electron, and in the object, the atom. 



SCATTERING OF 10,000 VOLT ELECTRONS^ 

 BY A HVOROSEN ATOM, 



— Morr- A/f/Assey formula, 

 Rutherford's la^. 



SCATTERISJO OF LIGHT, 



17 



10^ cmf 



ZXIO 



^17 



_^3x/0-'^ 



RAYLEIQH'S LAVS/. 



L4x/0-'^ 



Fig, 45. Scattering of light and of electrons 



