42 ORIGIN AND NATURE OF LIFE 



whole scale of the elements that it has been 

 the means of discovering many previously 

 unknown members. The properties and gene- 

 ral characteristics of a missing element have 

 even been fairly well described some years 

 before its actual discovery, much as a biologist 

 might describe a necessary missing species 

 in a biological group of living creatures. 

 As a result, the atomic weights of closely 

 related members of a chemical family do not 

 lie close together ; the relative atomic weights 

 of the elements, fluorine and iodine, for 

 example, are as 19 to 127, yet these belong 

 to the same natural group, and intermediately 

 are found chlorine at about 35 and bromine 

 at 87. The interesting point is, that between 

 the level of 19 and 35, in the value of the 

 relative weights of the atoms, the chemical 

 properties of the intermediately occurring 

 elements have run through the whole gamut 

 of all the chemical families which differ most 

 widely in chemical properties, but at 35 the 

 atomic circle has been completed, so to speak, 

 a kind of octave has occurred, and a higher 

 member of the original family has been 

 evolved. Space does not allow us to go into 

 this interesting law more fully here, for 

 information upon it, as also upon inorganic 

 evolution and the constitution of matter and 



