FIRE AS AN AGENT IN HUMAN CULTURE 193 



the worn expression, "if we had a considerable amount of radium" 

 something would come of it in the way of illumination, but not heat- 

 less light. 



It is not necessary that the light of the future should be without 

 heat, however much this feature might be desired. The requirement 

 appears to be the harnessing of a iotce now just out of our reach, but 

 which science sometimes feels is close in, which intensive work and 

 good fortune will put under our control. This desire to reach for 

 the key to the stronghold of illimitable force may be irrational, the 

 possession of the secret might lead to a world-enveloping catastrophe, 

 but when did science show fear in entering the arena of the unknown ? 



A fourth class, that of electricity, did not emerge in any encour- 

 aging degree till the latter part of the nineteenth century, when 

 mechanical technology began to furnish means for achievement of 

 electric lighting. Beginning with the arc, that wonderful discontin- 

 uity, there followed a bewildering series of inventions and improve- 

 ments which have given us our most modern light. The limits of 

 electric lighting, we may say with caution, appear to have been 

 visioned. It is probable that from this branch the lighting of the 

 future will not be derived. Up to this period all artificial light uti- 

 lized was yielded by the incandescence of particles of carbon in a 

 gaseous medium of high temperature. The early electric lights were 

 also of this class. There is about to be developed here illumination 

 not depending on this age-old feature. 



There is another class of substances of comparatively recent isola- 

 tion which give promise as to the light of the future. As a result of 

 extended experiments thorium oxide containing a trace of cerium was 

 made to produce the powerful radiations familiar in the Nernst and 

 mantle lamps, economically also in the latter by using the less-expen- 

 sive fuels as gas and coal oil, especially the latter. Certain other 

 chemical elements, such as calcium, magnesium, phosphorus, tungsten, 

 uranium, vanadium, etc., possess possibilities which have not been 

 fiUly explored. 



The present state of our knowledge of the nature of light repre- 

 sents a very marked advance. The chief feature which seems to be 

 estabhshed is that hght has mass. That it has the utmost conceiv- 

 able velocity possessed by matter in motion is not a novel statement. 

 Professor Langley's calculations that one thirty-quintilHonth of a 

 horsepower is capable of making us see sets a term to the natural 

 vision. It was also pointed out by Professor Langley that light as 

 produced by man is the result of a wasteful expenditure of power 

 from a human standpoint. This waste of energy is caused by the 

 necessity of bringing the emitting substance from normal to incan- 

 descence. Celestial light is seen to be the result of a prodigal expen- 

 diture of the ilhmitable forces of nature. 



