64 ORIGIN AND NATURE OF LIFE 



green light of the mercury arc lamp is another 

 example of a metallic arc which would give 

 the mercury spectrum. The spectrum given 

 by the electric potential of the ordinary voltaic 

 arc and produced at the high temperature of 

 this electric furnace, is not, however, the last 

 word as to what can be done in the way of 

 temporary disintegration of the more perma- 

 nent metallic elements into what have been 

 termed by Lockyer, proto-metals. 



Other forms of energy at a high pressure or 

 potential seem to possess a power of causing 

 atomic disintegration which heat alone does 

 not possess, for the electric pressure in the 

 ordinary arc-flame in air is so low compara- 

 tively, that the chemical effects Jiere must be 

 ascribed almost solely to the great heat pro- 

 duced in the crater of the arc by the conver- 

 sion of large quantities of electrical energy at 

 low pressure into heat. This operation is like 

 using the energy of a large river of water 

 falling only a small height. 



When, instead of the ordinary air-arc, 

 recourse is had to an arc in a high vacuum 

 spark-gap several inches in length across which 

 high tension electricity at an enormous pres- 

 sure of some hundreds of thousands of volts 

 is made to leap, then a new set of phenomena 

 at once make their appearance, and the 



