PHOSPHORESCENCE. 65 



taneous inflammation of phosphuretted hydrogen, 

 it could not be classed among phenomena of 

 phosphorescence any more than the flames of 

 certain fire-springs in the East, which are owing 

 to the combustion of carburetted hydrogen or 

 naphtha, and some of which, like the famous 

 Lycian Chimasra, in Asia Minor, have been burn- 

 ing for several thousand years. 



From some very interesting arguments brought 

 forward in the last edition (in one volume) of 

 Kirby and Spencers ' Introduction to Entomology,' 

 it would appear probable that some cases of ignis 

 fatuus might be attributed to certain luminous 

 insects not yet known, which hover in clusters 

 over marshy ground. These insects seem to be- 

 long to the genus Tipula (Gnat, " Daddy-Long- 

 legs," etc.), if we are to judge from the hovering 

 appearance of the light. Thus Dr. Derham, in the 

 ' Philosophical Transactions' for 1729, describes 

 an ignis fatuus, seen by himself, as flitting about 

 a thistle. 



Dr. Derham got within two or three yards of 

 another ignis fatuus, in spite of the boggy nature 

 of the soil. He states, however, that it appeared 

 like a complete body of light without any division, 

 so that he was sure it could not be occasioned by 

 insects. 



At the same time, it is evident that no insects 

 could produce the phenomenon described by Dr. 



p 



