LIFE AND LIGHT 33 



presence of highly organised plants containing chlorophyll and 

 responsive to the sun's rays. Such a high order of development 

 as that shown by the green plant could, however, almost certainly 

 not have constituted the beginning of all things living, as our earth 

 cooled down to the temperature at which bodies sufficiently complex 

 to form the habitation of biotic energy could without rapid com- 

 bustion exist upon its surface. 



The view that cosmic dust from another planet or astral body 

 first carried some biotic fragments or simple living organisms, 

 much as the winds might carry new species to a desert island and 

 start life there, carries us but little farther, for at a still more distant 

 epoch we are again met with the same difficulty of how life first 

 began from inorganic matter in that distant planet. 



The myth of spontaneous generation, of the type thought of 

 somewhat more than a generation ago by our forefathers, when 

 Pasteur waged warfare with this crudest doctrine of the origin of 

 living species, need only be mentioned to be dismissed, for such a 

 kind of spontaneous generation required organic matter for the 

 organisms to appear, and the problem we are facing now is that of 

 how, spontaneously or otherwise, organic matter arose endowed with 

 biotic energy in a world where there was no trace not merely of 

 living matter but no vestige of dead organic matter. Such a 

 world as that it is barely possible for us as inhabitants of this green 

 earth, covered with teeming energetic life, to realise or postulate 

 to ourselves. 



Yet in this dead inorganic world, somewhere about the time 

 when life, on account of temperature conditions, first became 

 possible, living creatures promptly, in the geological sense, became 

 present, as the record of the oldest sedimentary rocks teaches us 

 to-day. 



The degree of chemical complexity capable of existing in the 

 materials found on the earth is definitely fixed by temperature. At 

 a white heat (for example, at such a heat as exists in the sun's 

 atmosphere) only such forms of matter as we term elements can 

 remain in equilibrium, and probably many of these decompose just 

 as radium goes on decomposing at ordinary earth atmospheric 

 temperatures. At a somewhat lower temperature binary compounds, 

 such as oxides, can remain stable in a condition of equilibrium with 

 either complete or incomplete combination. Lower still in the 

 temperature scale, saline compounds of the halogens, and of 



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