FROM DUST TO DUST. 59 



but very incompletely effected ; and our old friend Bacterium 

 iermo, or Bacillus proteus, as he is now called, ultimately finishes 

 the business. Were it not for this;, certain substances would assume 

 a state of rest, and be incapable of being again used ; whilst the 

 earth's surface would be littered and clogged wnth dead and useless 

 organic matter, and all life, as we now know it, would cease to exist. 

 Animal decomposition comes to an end only with the change of 

 the last particle of organic matter into the inorganic, when chemical 

 decomposition and mechanical dismtegration restore the mineral 

 and gaseous elements to the condition of being capable to live 

 again. It is quite possible that in some instances a " short circuit " 

 is made, but our present teaching tends more and 'more to show 

 that all life — as first life must have been — is built u[) from elemen- 

 tary particles, such as nitrogen, carbon, silicon, water, nutrient 

 salts or mineral food stuffs, such as the soluble sulphates, phos- 

 phates, nitrates, and chlorides of calcium, magnesium, sodium, 

 potassium, and iron ; whilst for plants living in the sea, iodine 

 and bromine are of especial importance. Fluorine, manganese, 

 lithium, and various other metals, such as alumina, found in the 

 ash of lycopodium, also enter upon their cycle through life by 

 means of plants. 



Cyclical change thus appears to be the key-note which domin- 

 ates all the harmonies of Nature. 



SUMMARY. 



I have made the attempt to show how the study of Nature — 

 having especial regard to the phenomena of life — to which we give 

 the comprehensive title " Biology," embraces and binds all other 

 Sciences together. 



How the thoughts of many minds have been crystallised into 

 that priceless pearl of knowledge, "The Theory of Evolution." 



How the discovery, in our own times, of the hithero unknown 

 world of micro-organisms had thrown its light on this, and many 

 of life's deepest mysteries. 



How the conditions of life existence — the formation of soil — 

 preceded all evolution of life. 



How organisms turned inorganic material into protoplasmic 

 life, but 



