THE PURPOSE OF DIVERSITY 387 



advance of chemical science, the knowledge that has been 

 obtained of the inner nature of the best-known older 

 elements, the wonderfully complex laws of their combinations, 

 and the immense variety of their known compounds, our 

 ever-increasing knowledge of the complexity of matter will 

 be very much greater. 



During the early part of the nineteenth century, the 

 old idea of atoms as being indivisible, incompressible, and 

 indestructible particles, almost universally prevailed. They 

 were usually supposed to be spherical in form, and to be 

 the seat of both attractive and repulsive forces, leading to 

 cohesion and chemical combination. Those of the different 

 elements were supposed to differ slightly in size and in 

 energy, which led to their differences of weight and other 

 properties. The whole conception, though we now see it to 

 be totally inadequate, was comparatively simple, and with 

 the help of the mysterious electric and magnetic forces 

 seemed capable of explaining much. 



But, decade after decade, fresh discoveries were made ; 

 chemical theory became more and more complex ; electricity, 

 the more it was known the less intelligible it became ; while 

 a host of new discoveries in the radiant forces of the ether 

 seemed to show that this mysterious substance was really 

 the seat of all the forces of the universe, and that the various 

 basic forms of matter which we term elements were nothing 

 more than the special manifestation of those forces. It thus 

 became evident that all our progress in physical science 

 rendered the world of matter far more wonderful, and at the 

 same time less intelligible than it had ever seemed to us 

 before. 1 



1 The progress of modern chemistry well shows this increasing complexity 

 with increasing knowledge. The fact of carbon existing in three distinct forms 

 — charcoal, graphite, and diamond, each with its own special physical and 

 chemical characters — has already been referred to. But it is found that many 

 other elements have similar properties, especially silicon, phosphorus, arsenic, 

 antimony, sulphur, oxygen, and several others. This curious property is termed 

 allotropy ; and it seems somewhat analogous to that property of many compound 

 substances termed isomerism, of which two striking examples were given at the 

 beginning of the last chapter. Another modern branch of chemistry is the study 

 of the relation of crystallised substances to polarised light, which reveals many 

 new and strange properties of identical compounds, and is termed Stereo- 

 chemistry. 



These various properties of the atoms and molecules of matter have so 

 complicated their relations, that the attempt to unravel them has led to a 



