xviii THE ELEMENTS AND LIFE 363 



two latter withstand all temperatures, except the very 

 highest obtainable. These various states of carbon differ 

 in other respects. Ordinary carbon is a good conductor of 

 electricity ; the diamond is a non-conductor. 



Carbon unites chemically with almost all the other 

 elements, either directly or by the intervention of some of 

 the gases. It also possesses, as Sir Henry Roscoe says : " A 

 fundamental and distinctive quality. This consists in the 

 power which this element possesses, in a much higher degree 

 than any of the others, of uniting with itself to form com- 

 plicated compounds, containing an aggregation of carbon- 

 atoms united with either oxygen, hydrogen, nitrogen, or 

 several of these, bound together to form a distinct chemical 

 whole." 



Carbon is also the one element that is never absent from 

 any part or product of the vegetable or animal kingdoms ; 

 and its more special property is that, when combined with 

 hydrogen, nitrogen, and oxygen, together with a small 

 quantity (about I per cent) of sulphur, it forms the whole 

 group of substances called albuminoids (of which white of 

 egg is the type), and which, much diluted, forms the essential 

 part of the blood, from which all the solids and fluids of 

 organisms are secreted. It was on these special features of 

 carbon that Haeckel founded his celebrated carbon-theory of 

 life, which he has thus stated : " The peculiar chemico- 

 physical properties of carbon — especially the fluidity and 

 the facility of decomposition of the most elaborate albuminoid 

 compounds of carbon — are the sole and the mechanical 

 causes of the specific phenomena of movement, which dis- 

 tinguish organic from inorganic substances, and which are 

 called life, in the usual sense of the word." And he adds : 

 " Although this ' carbon-theory ' is warmly disputed in some 

 quarters, no better monistic theory has yet appeared to 

 replace it." 



What a wonderfully easy way of explaining a mystery ! 

 Carbon forms a constituent of the bodies and of the products 

 of all living things ; therefore carbon is the cause of life 

 and all its phenomena ! 



But besides the carbon in the atmosphere an immense 

 quantity exists in the various limestone rocks, consisting of 



