OTe | 
ever, containing the radical of water: 
Yor, if condensation of the resulting water 
did contemporaneously occur, the light 
wielded would be unprofitable for all 
economical purposes, as it is essential in 
all usefel illumination, that the light 
should be unclouded, and that the light 
producing points should not exhibit a sort 
ef kulos between them and the specta- 
_ tor’s eye. We know it has been assert- 
‘ed, that when carburetted hydrogen has 
been used to any vreat extent, fas in the 
ease of the gaselights, which we have had 
such frequent e@pportunities of ,witness- 
mg,) that the cloaks, perriwigs, furs, &c. 
of the spectators, have been seen to be 
surrounded by tears ef dew, from the 
aqueous condensation produced. But if 
this effect has cver occurred, it must 
have been under very particular circum- 
stances, and only when the lights were 
far more numerous than could be con- 
sistent with profit or advantage to the 
rooms where they were intended to be 
useful, or ornamental. ~All exceilence 
has its limits ; 
_ & Sunt certi denique fines, &c.” 
We should be rather inclined to ima- 
gine, that, in the instances alluded to, 
the halitus of the expiration from the 
lungs furnished the principle of moisture, 
rather than any actual deposition from 
the atmosphere, from the products of 
combustion alluded to, because they 
never occur in apartments ventilated. 
I shall not treuble you much longer, 
Mr. Editor, but simply wish to preseut 
a few remarks on that part of Dr. Jones’s 
eommunication, in which he says, “ It 
Fs not unusual for the gas ‘o take fire from 
the lighted candles attempted to be in- 
troduced into the works: the damp, on 
such occasions, burns with a blue flame, 
explosions ensue, and very often the mi- 
ners in the work, and the winders at the 
mouth of the pit, fall victims to this in- 
evitable catastrophe. The coal mines 
belonging to Lord Cawdor, at Lanlash, 
tn Carmarthenshire, were, about a month 
past, annoyed with this damp, which 
rendered the miners heavy and sleepy, 
and made it impossible for them to keep 
im their lights. Seing informed of the 
circumstance by William Datydd,- of 
Tuyha, the present overseer of the works, 
¥ requested him to slacken a few lumps 
of fresh lime in the level, or subterra- 
neous passage made by the miners in 
digging out the coals; having anidea that 
the carbonic acid gas, produced by 
throwing a few lumps of lime into a little 
water, would correct the air in the 
Erroneous Account of the Gum Beetle. 
[Jan. I, : 
works, and make it more favourable to 
inhalation and combustion. The over- 
seer complied with my request, and sent 
me word next day, that the experiment 
was attended with success, and the mi- 
ners enabled to go on with the works. 
The prevalence of the damp in coal 
mines is so general, and its effects so dan- 
gerous by privation of lives, that I (Dr. 
Jones) conceived this success, in apply-_ 
ing a cheap and rational remedy, should 
be known to the public.” 
Then, Mr. Editor, is it not very new 
to tell us, that the same quality of lime, 
upon this occasion, depends upon the 
quantity of fine carbonic acid gas which 
it yields during its being slacked, or pul- 
verized, by its chemical avidity for 
water? Are we to suppose, that there 
is any disengagement whatever from the 
lime, that could, with reference to the 
methodus medendi, or its healing qualities, 
or corrective powers, upon the mephitic, 
compound, choak, and fire damp, 1” the 
mine, depend upon any such principle 
as that to which the author alludes ? 
To be brief—The true reason is, that 
the disengagement of heat, and conse- 
quent expansion, or circulation, or €x- 
citement, of draught, as it is mistakenly 
named, is ereated. Proper respirable 
air occupies the space of these Lethean 
deletereous vapours ; and itis of little eon- 
sequence, whether expansion be effected 
by the hkerated caloric, disaggregated 
line, or a similar principle, furnished 
by means decidedly distinct—the hbe- 
rated heat of combustion. All of us 
know the ordinary care of the miner, OF 
the mode of freeing his pits from foul air, 
which is to excite by air-shafts circula- 
tion, these being corrected with perpe= 
tual and rousing fires. 
Your's, &c. im 
N.B. Qu. Is not the term ¢¢ rousing” as 
applied to fire {and as to its etymology ) clear- 
ly pointed out from the creation of circu- 
lation of theair of any particular confined 
region? ‘. 
eee 
To the Editor of the Monthly Magazine, 
SIR, RACK 
S I have long been in the habit of 
paying attention to the Insect 
World, I was struck in reading lately 
an Account of Morocco, by a Mr. Jack- 
son, with his statement respecting a / 
Beetle, which, he says, is the only other» 
animal, except the vulture, that is found 
near the tree producing gum ammoniac 5 
and of the production of which it is im 
fact the cause, by making in the tree, 
with 
