FINAL DEDUCTIONS. 



93 



vital fluid in the animal is low-temperature combustion 

 or other chemical action, and that a system of direct 

 conversion is there in operation. 



Scientific men are somewhat more familiar with the 

 case of the firefly, curiously enough ; that is to say, 

 the production of light without heat, as well as the 

 transformation of energies resulting in the economical 

 production of heat and power in the animal system. 

 It has long been known that certain chemical com- 

 pounds, notably fats containing sulphur and phospho- 

 rus, may be burned at exceedingly low temperatures, 

 with an evolution of a mild light almost or quite 

 entirely free from heat. Some such compounds are 

 found in nature, and the chemist has artificially pro- 

 duced others. He finds that he may at will produce, 

 in some cases, slow and cold hght-production or rapid 

 and heat-producing oxidation. Numerous experiments 

 upon the firefly and the glowworm indicate that theirs 

 is a light thus obtained. This so-called " phosphores- 

 cence" is seen in many insects, worms, fishes, and 

 mollusks, and even in vegetable and mineral matter. 

 For a century this investigation has been in progress, 

 and it is well established that the low-temperature 

 combustion of a peculiar substance, given form in the 

 body of the firefly, for instance, by peculiar organs 

 specially constituted for that purpose, results in the 

 production of light without heat. This has been most 

 recently and most conclusively proved by Messrs. 

 Langley and Very, who show by actual measurement 

 with the Langley " bolometer," an instrument capable 

 of measuring even the heat received from the moon, 

 that insect light " is accompanied by approximately 

 one four-hundredth part of the heat which is ordinarily 



