10 
THE CABINET OF NATURAL HISTORY, 
well-defined horizontal line eight or nine inches above it, 
appeared moist, and on stepping in, I immediately became 
sensible of a small degree of warmth up to the same height, 
although the atmosphere down to the ground was perfectly 
transparent. The custode first directed me to get on my 
hands and knees, and to bring my face within the influ- 
ence of the gas. I took the posture desired, and as I had 
lowered my head to within a short distance of the ground, 
and found myself breathing a pure aft, was beginning to 
think the wonders of the grotto far overrated, when I sud- 
denly found myself bolt upright, and on my feet, having- 
been brought there by a sensation as if a thousand needles 
had been at once thrust into my nostrils. The feeling was 
like that often experienced after drinking strong soda water, 
only to an almost overpowering degree. 
The next experiment was a cruel one, but I hope par- 
donable, inasmuch as the cruelty was far from being of 
a wanton kind. The man looked for a dog which he had 
brought with him, and tied to some bushes near the door, 
and taking the struggling animal in his arms laid him down 
in the deepest part of the cave. The dog laid quiet for 
a moment, and then, with a sudden start nearly escaped 
from the custode’s hands, but was brought back, and once 
more held down within the full power of the gas. His 
struggles were violent, and his eyes turned upward toward 
his master, showed a high degree of suffering; but present- 
ly, his muscles began to relax, and his struggles ceased, 
his open and beseeching eye only showing life. His 
master now took him up, and laid him in the pure air, 
outside the cave. Here he remained motionless for nearly 
two minutes, when he was seized with violent spasms, 
gasped for breath; at length got on his feet, staggered 
about, and then recovering himself fully, darted away 
into the bushes. A whistle brought him back, and he 
came up, wagging his tail, to receive the customary crust 
of bread. The man now lighted a couple of torches, and 
placing one in my hand, allowed me to amuse myself with 
such experiments as are frequently practised in our La- 
boratories with this gas, and others of a similar character. 
The flame began to separate from the torch as soon as it 
was lowered to the line noticed above, showing a smooth 
uniform surface to the gas. When moved along the sill 
of the door, it burnt with undiminished brightness, except 
where a small channel was made by an inequality in the 
wood; Avhen it sunk into this the light was immediately 
extinguished. In the same manner, I could discern the 
gas flowing down the hollows leading from this to the lake. 
When I had satisfied myself with these experiments, the 
custode took both the torches, and rubbing them against 
the sides of the cave, filled the bottom of it with smoke; 
the hitherto invisible spirit of the cave took form and sub- 
stance; and I was warned by a gentle hint, for half a dollar, 
that the exhibition was at an end. — Silliman’s Journal . 
OBSERVATIONS ON IGNIS FATUUS. 
By Rev John Mitchell. 
Those luminous appearances, which are popularly called 
“ Will-o’the-wisp” and “ Jack-a-lantern,” have been alike 
the object of vulgar superstition and philosophical curiosi- 
ty; and notwithstanding all attempts to apprehend and 
subject them to examination, they are not much more the 
subjects of knowledge now than they were centuries ago. 
They are still but an ignis fatuus to the philosopher, and a 
thing of mystery to the credulous. 
I was myself, formerly familiar with these appearances; 
they were of frequent occurrence near my father’s resi- 
dence, owing probably, to the proximity of extensive wet 
grounds, over which they are usually seen. The house 
stood upon a ridge, which sloped down on three sides to 
the beautiful meadows which form the margin of the Con- 
necticut, and off its tributary creeks, and which, owing to 
their own luxuriance and the deposits of the vernal 
freshets, are covered with rich and constantly decaying 
vegetable matter. From the circumstance, also, that we 
had no neighbours in the direction of these grounds, a 
light could not be seen over them without attracting our 
notice. I mention this by way of suggesting, that pro- 
bably the ignis fatuus, in consequence of its not being al- 
ways distinguished from the lights of surrounding houses, 
and therefore exciting no curiosity, is oftener seen than it 
is supposed to be. 
These mysterious luminaries used often to be seen by 
the fishermen; who plied their nets by night as well as by 
day. They commonly reported that they saw them a 
little above the surface of the meadow, dancing up and 
down, or gliding quietly along in a horizontal line. Some- 
times two, or even three, would be seen together, skip- 
ping and dancing or sailing away in concert, as if rejoic- 
ing in their mutual companionship. I might entertain 
you with abundance of fabulous accounts of them — the 
offspring of imaginations tinctured with superstition, and 
of minds credulous from a natural love of the marvellous. 
Fables, however, are of little value for the purposes of 
science: if the following account of some of the pheno- 
mena of the ignis fatuus, shall, with the observations of 
others, contribute towards a true theory of its nature, you 
will think them worthy of a place in your Journal. 
A friend of mine, returning from abroad late in the 
