PHOSPHORESCENCE. 65 
taneous inflammation of phosphuretted hydrogen, 
it could not be classed among phenomena of 
phosphorescence any more than the flames of 
certain jire-springs in the Kast, which are owing 
to the combustion of carburetted hydrogen or 
naphtha, and some of which, like the famous 
Lycian Chimeera, 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 Spence’s ‘ 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 hght. Thus Dr. Derham, in the 
‘Philosophical Transactions’ for 1729, describes 
an ignis fatwus, seen by himself, as flittmg about 
a thistle. 
Dr. Derham got within two or three yards of 
another ignis fatwus, 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 vt could not be occasioned by 
insects. 
At the same time, it 1s evident that no insects 
could produce the phenomenon described by Dr. 
EF 
