PHOSPHORESCENCE. 69 
he went out of the room, but the natural pheno- 
menon generally recedes as we approach it. 
It is acommon practice, in chemical lectures, to 
imitate the Will-o’-the-wisp by throwing fragments 
of phosphuret of calciwm mto water, when flames 
arise, owing to the spontaneous combustion of 
phosphuretted hydrogen gas. But the imitation 
is very bad indeed, and can hardly be said to 
resemble the mysterious natural phenomenon, 
much less explain it. For my own part, I think 
the igiis fatwus to be sometimes the light from a 
burning gas, which light is mvisible in the day- 
time, and at other times to be connected with 
those curious cases of luminous mists mentioned 
above, and in which electricity doubtless plays an 
important part. 
The luminous appearances known in Scotland 
as Lilf-candles belong either to this category of 
phenomena, or to that which will be treated of in 
a future chapter of this Work. 
