THE ELEME:N^TS AXD life 387 



The two elements in italics — iiilicoit and Alumijiiuni — altlioiii:li form- 

 ing a large proportion of the earth's substance, are not ctmcndal constitu- 

 ents of protophism, although occasionally forming part of it. 



In the list of the more important elements here given, I 

 have arranged them in two series, the first showing the essential 

 constituents of protoplasm ; the second showing the ten which 

 are the most important constituents of the earth's mass as 

 known to geologists and physicists. The four which are itali- 

 cised in the first list do not appear in the second, and cannot, 

 therefore, be considered as forming an essential portion of the 

 rock-structure of the earth, although without them it seems 

 fairly certain that the life-world could not have existed. 



The Elements in relation to Man 



So far as we can see, therefore, the fourteen elements in 

 these two lists would have sufficed to brine: about all the essen- 

 tial features of our earth as w^e now find it. All the others 

 (more than sixty) seem to be surplusage, many exceedingly 

 rare, and none forming more than a minute fraction of the 

 mass of the earth or its atmosphere. All except seven of these 

 are metals, including (with iron) the seven metals known to 

 the ancients and even to some prehistoric races. The seven 

 ancient metals are gold, silver, copper, iron, tin, lead, and mer- 

 cury. All of these are widely distributed in the rocks. They 

 are most of them found occasionally in a pure state, and are 

 also obtained from their ores without much difficulty, which 

 has led to their being utilised from very early times. But 

 though these metals (except iron) appear to serve no important 

 purpose either in the earth itself or in tlie vegetable or animal 

 kingdoms, they have yet been of very gTcat importance in the 

 history of man and the development of civilisation. From very 

 remote times gold and silver have been prized for their extreme 

 beauty and comparative rarity; the search after them has led 

 to the intercourse between various races and peoples, and to 

 the establishment of a world-wide conmierce ; wliile the facility 

 W'ith wdiich they could be worked and polished called fortli the 



