CHAP. 32] THE ORIGIN OF LIFE 853 



Cosmic-ray energy is negligible at present, and there is no reason to assume 

 it was greater in the past. The radioactive disintegration of uranium, thorium 

 and potassium was more important 4.5 x 10^ years ago, but still the energy was 

 largely expended on the interior of solid materials of the rocks, and only a very 

 small fraction of the total energy was available in the oceans and atmosphere. 

 Volcanic energy is not only small but its availability is very low. A continuous 

 source of energy is needed. It contributes little to the evolutionary process to 

 have a lava flow in one part of the Earth at one time and to have another flow 

 on the opposite side of the Earth years later. For a brief time heat is available 

 at the surface of the lava, but the surface cools and heat flows slowly from the 

 interior for years, giving a slightly warmer surface. Only a very small contri- 

 bution to the evolutionary process could be contributed by these energy sources. 



3. The Synthesis of Organic Compounds 



A. Electric Discharges 



While ultraviolet light is a greater source of energy than electric discharges, 

 the greatest progress in the synthesis of organic compounds under primitive 

 conditions has been made with electric discharges. The apparatus used by 

 Miller in these experiments was a closed system of glass, except for tungsten 

 electrodes. The water is boiled in a 500-ml flask which mixes the water vapor 

 and gases in a 5-1. flask where the spark is located. The products of the discharge 

 are condensed and flow through the U-tube back into the small flask. The first 

 report (Miller, 1953) showed that when methane, ammonia, water and hydrogen 

 were subjected to a high-frequency spark, milligram quantities of glycine, 

 alanine and a-amino-n-butyric acid were produced. A more complete analysis 

 (Miller, 1955, 1957) of the products gave the results shown in Table II. The 

 compounds in the table account for 15% of the carbon as methane, with the 

 yield of glycine alone being 2.1%. Indirect evidence indicated that polyhydroxyl 



Table II 



Yields in moles ( x 10^) from Sparking a Mixture of CH4, NH3, H2O and H2. 



710 mg of Carbon was added as CH4. 



