this interesting and curious branch of Physics; in which the friendship
of Dr. Priestley first engaged me, in concert with himself.

                                      Manchester, March 16, 1774.

In a course of Experiments, which is yet unfinished, I have had frequent
opportunities of observing that FIXED AIR may in no inconsiderable
quantity be breathed without danger or uneasiness. And it is a
confirmation of this conclusion, that at Bath, where the waters
copiously exhale this mineral spirit,[15] the bathers inspire it with
impunity. At Buxton also, where the Bath is in a close vault, the
effects of such _effluvia_, if noxious, must certainly be perceived.

Encouraged by these considerations, and still more by the testimony of a
very judicious Physician at Stafford, in favour of this powerful
antiseptic remedy, I have administered fixed air in a considerable
number of cases of the PHTHISIS PULMONALIS, by directing my patients to
inspire the steams of an effervescing mixture of chalk and vinegar; or
what I have lately preferred, of vinegar and potash. The hectic fever
has in several instances been considerably abated, and the matter
expectorated has become less offensive, and better digested. I have not
yet been so fortunate in any one case, as to effect a cure; although the
use of mephitic air has been accompanied with proper internal medicines.
But Dr. Withering, the gentleman referred to above, informs me, that he
has been more successful. One Phthisical patient under his care has by a
similar course intirely recovered; another was rendered much better; and
a third, whose case was truly deplorable, seemed to be kept alive by it
more than two months. It may be proper to observe that fixed air can
only be employed with any prospect of success, in the latter stages of
the _phthisis pulmonalis_, when a purulent expectoration takes place.
After the rupture and discharge of a VOMICA also, such a remedy promises
to be a powerful palliative. Antiseptic fumigations and vapours have
been long employed, and much extolled in cases of this kind. I made the
following experiment, to determine whether their efficacy, in any
degree, depends on the separation of fixed air from their substance.

One end of a bent tube was fixed in a phial full of lime-water; the
other end in a bottle of the tincture of myrrh. The junctures were
carefully luted, and the phial containing the tincture of myrrh was
placed in water, heated almost to the boiling point, by the lamp of a
tea-kettle. A number of air-bubbles were separated, but probably not of
the mephitic kind, for no precipitation ensued in the lime water. This
experiment was repeated with the _tinct. tolutanæ, ph. ed._ and with
_sp, vinos. camp._ and the result was entirely the same. The medicinal
action therefore of the vapours raised from such tinctures, cannot be
ascribed to the extrication of fixed air; of which it is probable bodies
are deprived by _chemical solution_ as well as by _mixture_.

If mephitic air be thus capable of correcting purulent matter in the
lungs, we may reasonably infer it will be equally useful when applied
externally to foul ULCERS. And experience confirms the conclusion. Even
the sanies of a CANCER, when the carrot poultice failed, has been
sweetened by it, the pain mitigated, and a better digestion produced.
The cases I refer to are now in the Manchester infirmary, under the
direction of my friend Mr. White, whose skill as a surgeon, and
abilities as a writer are well known to the public.

Two months have elapsed since these observations were written,[16] and
the same remedy, during that period, has been assiduously applied, but
without any further success. The progress of the cancers seems to be
checked by the fixed air; but it is to be feared that a cure will not be
effected. A palliative remedy, however, in a disease so desperate and
loathsome, may be considered as a very valuable acquisition. Perhaps
NITROUS AIR might be still more efficacious. This species of factitious
air is obtained from all the metals except zinc, by means of the nitrous
acid; and Dr. Priestley informs me, that as a sweetener and antiseptic
it far surpasses fixed air. He put two mice into a quantity of it, one
just killed, the other offensively putrid. After twenty-five days they
were both perfectly sweet.

In the ULCEROUS SORE THROAT much advantage has been experienced from the
vapours of effervescing mixtures drawn into the _fauces_[17]. But this
remedy should not supersede the use of other antiseptic
applications.[18]

A physician[19] who had a very painful APTHOUS ULCER at the point of his
tongue, found great relief, when other remedies failed, from the
application of fixed air to the part affected. He held his tongue over
an effervescing mixture of potash and vinegar; and as the pain was
always mitigated, and generally removed by this vaporisation, he
repeated it, whenever the anguish arising from the ulcer was more than
usually severe. He tried a combination of potash and oil of vitriol well
diluted with water; but this proved stimulant and increased his pain;
probably owing to some particles of the acid thrown upon the tongue, by
the violence of the effervescence. For a paper stained with the purple
juice of radishes, when held at an equal distance over two vessels, the
one containing potash and vinegar, the other the same alkali and
_Spiritus vitrioli tenuis_, was unchanged by the former, but was spotted
with red, in various parts, by the latter.

In MALIGNANT FEVERS wines abounding with fixed air may be administered,
to check the septic ferment, and sweeten the putrid _colluvies_ in the
_primæ viæ_. If the laxative quality of such liquors be thought an
objection to the use of them, wines of a greater age may be given,
impregnated with mephitic air, by a simple but ingenious contrivance of
my friend Dr. Priestley.[20]

The patient's common drink might also be medicated in the same way. A
putrid DIARRH[OE]A frequently occurs in the latter stage of such
disorder, and it is a most alarming and dangerous symptom. If the
discharge be stopped by astringents, a putrid _fomes_ is retained in the
body, which aggravates the delirium and increases the fever. On the
contrary, if it be suffered to take its course, the strength of the
patient must soon be exhausted, and death unavoidably ensue. The
injection of mephitic air into the intestines, under these
circumstances, bids fair to be highly serviceable. And a case of this
deplorable kind, has lately been communicated to me, in which the vapour
of chalk and oil of vitriol conveyed into the body by the machine
employed for tobacco clysters, quickly restrained the _diarrhoea_,
corrected the heat and foetor of the stools, and in two days removed
every symptom of danger[21]. Two similar instances of the salutary
effects of mephitic air, thus administered, have occurred also in my own
practice, the history of which I shall briefly lay before the reader.
May we not presume that the same remedy would be equally useful in the
DYSENTERY? The experiment is at least worthy of trial.

Mr. W----, aged forty-four years, corpulent, inactive, with a short
neck, and addicted to habits of intemperance, was attacked on the 7th of
July 1772, with symptoms which seemed to threaten an apoplexy. On the
8th, a bilious looseness succeeded, with a profuse hoemorrhage from
the nose. On the 9th, I was called to his assistance. His countenance
was bloated, his eyes heavy, his skin hot, and his pulse hard, full, and
oppressed. The diarrhoea continued; his stools were bilious and very
offensive; and he complained of griping pains in his bowels. He had
lost, before I saw him, by the direction of Mr. Hall, a surgeon of
eminence in Manchester, eight ounces of blood from the arm, which was of
a lax texture; and he had taken a saline mixture every sixth hour. The
following draught was prescribed, and a dose of rhubarb directed to be
administered at night.

      Rx. _Aq. Cinnam. ten._        oz. j.
     _Succ. Limon. recent._         oz. ß.
     _Salis Nitri gr. xij. Syr. è Succo Limon. dr. j. M. f. Haust._
     _4tis horis sumendus._

July 11. The _Diarrhoea_ was more moderate; his griping pains were
abated; and he had less stupor and dejection in his countenance. Pulse
90, not so hard or oppressed. As his stools continued to be foetid,
the dose of rhubarb was repeated; and instead of simple cinnamon-water,
his draughts were prepared with an infusion of columbo root.

12. The _Diarrhoea_ continued; his stools were involuntary; and he
discharged in this way a quantity of black, grumous, and foetid blood.
Pulse hard and quick; skin hot; tongue covered with a dark fur; abdomen
swelled; great stupor. Ten grains of columbo root, and fifteen of the
_Gummi rubrum astringens_ were added to each draught. Fixed air, under
the form of clysters, was injected every second or third hour; and
directions were given to supply the patient plentifully with water,
artificially impregnated with mephitic air. A blister was also laid
between his shoulders.

13. The Diarrhoea continued, with frequent discharges of blood; but
the stools had now lost their foetor. Pulse 120; great flatulence in
the bowels, and fulness in the belly. The clysters of fixed air always
diminished the tension of the _Abdomen_, abated flatulence, and made the
patient more easy and composed for some time after their injection. They
were directed to be continued, together with the medicated water. The
nitre was omitted, and a scruple of the _Confect. Damocratis_ was given
every fourth hour, in an infusion of columbo root.

14. The Diarrhoea was how checked, His other symptoms continued as
before. Blisters were applied to the arms; and a drachm and a half of
the _Tinctura Serpentariæ_ was added to each draught.

15. His pulse was feeble, quicker and more irregular. He dosed much;
talked incoherently; and laboured under a slight degree of _Dyspnæa_.
His urine, which had hitherto assumed no remarkable appearance, now
became pale. Though he discharged wind very freely, his belly was much
swelled, except for a short time after the injection of the
air-clysters. The following draughts were then prescribed.

     Rx _Camphoræ mucilag. G. Arab, solutæ gr. viij. Infus. Rad.
     Columbo oz. jfs Tinct. Serpent. dr. ij Confect. Card.
     scruple j Syr. è Cort. Aurant dr. i m. f. Haust. 4tis horis
     sumendus._

Directions were given to foment his feet frequently with vinegar and
warm water.

16. He has had no stools since the 14th. His _Abdomen_ is tense. No
change in the other symptoms. The _Tinct. Serpent._ was omitted in his
draughts, and an equal quantity of _Tinct. Rhæi Sp._ substituted in its
place.

In the evening he had a motion to stool, of which he was for the first
time so sensible, as to give notice to his attendants. But the
discharge, which was considerable and slightly offensive, consisted
almost entirely of blood, both in a coagulated and in a liquid state.
His medicines were therefore varied as follows:

     Rx. _Decoct. Cort. Peruv. oz. iss Tinct. Cort. ejusd. dr. ij. Confect.
     Card. scruple j Gum. Rubr. Astring. gr.
     xv. Pulv. Alnmin. gr. vij. m. f. Haustus 4tis horis
     sumendus._

Red Port wine was now given more freely in his medicated water; and his
nourishment consisted of sago and salep.

In this state, with very little variation, he continued for several
days; at one time ostive, and at another discharging small quantities of
fæces, mixed with grumous blood. The air-clysters were continued, and
the astringents omitted.

20. His urine was now of an amber colour, and deposited a slight
sediment. His pulse was more regular, and although still very quick,
abated in number ten strokes in a minute. His head was less confused,
and his sleep seemed to be refreshing. No blood appeared in his stools,
which were frequent, but small in quantity; and his _Abdomen_ was less
tense than usual. He was extremely deaf; but gave rational answers to
the few questions which were proposed to him; and said he felt no pain.

21. He passed a very restless night; his delirium recurred; his pulse
beat 125 strokes in a minute; his urine was of a deep amber colour when
first voided; but when cold assumed the appearance of cow's whey. The
_Abdomen_ was not very tense, nor had he any further discharge of blood.

Directions were given to shave his head, and to wash it with a mixture
of vinegar and brandy; the quantity of wine in his drink was diminished;
and the frequent use of the pediluvium was enjoined. The air-clysters
were discontinued, as his stools were not offensive, and his _Abdomen_
less distended.

22. His pulse was now small, irregular, and beat 130 strokes in a
minute. The _Dyspnoea_ was greatly increased; his skin was hot, and
bedewed with a clammy moisture; and every symptom seemed to indicate the
approach of death. In this state he continued till evening, when he
recruited a little. The next day he had several slight convulsions. His
urine which was voided plentifully, still put on the appearance of whey
when cold. Cordial and antispasmodic draughts, composed of camphor,
tincture of castor, and _Sp. vol. aromat._ were now directed; and wine
was liberally administered.

24. He rose from his bed, and by the assistance of his attendants walked
across the chamber. Soon after he was seized with a violent convulsion,
in which he expired.

To adduce a case which terminated fatally as a proof of the efficacy of
any medicine, recommended to the attention of the public, may perhaps
appear singular; but cannot be deemed absurd, when that remedy answered
the purposes for which it was intended. For in the instance before us;
fixed air was employed, not with an expectation that it would cure the
fever, but to obviate the symptoms of putrefaction, and to allay the
uneasy irritation in the bowels. The disease was too malignant, the
nervous system too violently affected, and the strength of the patient
too much exhausted by the discharges of blood which he suffered, to
afford hopes of recovery from the use of the most powerful antiseptics.

But in the succeeding case the event proved more fortunate.

Elizabeth Grundy, aged seventeen, was attacked on the 10th of December
1772, with the usual symptoms of a continued fever. The common method of
cure was pursued; but the disease increased, and soon assumed a putrid
type.

On the 23d I found her in a constant delirium, with a _subsultus
tendinum_. Her skin was hot and dry, her tongue black, her thirst
immoderate, and her stools frequent, extremely offensive, and for the
most part involuntary. Her pulse beat 130 strokes in a minute; she dosed
much; and was very deaf. I directed wine to be administered freely; a
blister to be applied to her back; the _pediluvium_ to be used several
times in the day; and mephitic air to be injected under the form of a
clyster every two hours. The next day her stools were less frequent, had
lost their foetor, and were no longer discharged involuntarily; her
pulse was reduced to 110 strokes in the minute; and her delirium was
much abated. Directions were given to repeat the clysters, and to supply
the patient liberally with wine. These means were assiduously pursued
several days; and the young woman was so recruited by the 28th, that the
injections were discontinued. She was now quite rational, and not averse
to medicine. A decoction of Peruvian bark was therefore prescribed, by
the use of which she speedily recovered her health.

I might add a third history of a putrid disease, in which the mephitic
air is now under trial, and which affords the strongest proof both of
the _antiseptic_, and of the _tonic_ powers of this remedy; but as the
issue of the case remains yet undetermined (though it is highly
probable, alas! that it will be fatal) I shall relate only a few
particulars of it. Master D. a boy of about twelve years of age, endowed
with an uncommon capacity, and with the most amiable dispositions, has
laboured many months under a hectic fever, the consequence of several
tumours in different parts of his body. Two of these tumours were laid
open by Mr. White, and a large quantity of purulent matter was
discharged from them. The wounds were very properly treated by this
skilful surgeon, and every suitable remedy, which my best judgment could
suggest, was assiduously administered. But the matter became sanious, of
a brown colour, and highly putrid. A _Diarrhoea_ succeeded; the
patient's stools were intolerably offensive, and voided without his
knowledge. A black fur collected about his teeth; his tongue was covered
with _Aphthæ_; and his breath was so foetid, as scarcely to be
endured. His strength was almost exhausted; a _subsultus tendinum_ came
on; and the final period of his sufferings seemed to be rapidly
approaching. As a last, but almost hopeless, effort, I advised the
injection of clysters of mephitic air. These soon corrected the foetor
of the patient's stools; restrained his _Diarrhoea_; and seemed to
recruit his strength and spirits. Within the space of twenty-four hours
his wounds assumed a more favourable appearance; the matter discharged
from them became of a better colour and consistence; and was no longer
so offensive to the smell. The use of this remedy has been continued
several days, but is now laid aside. A large tumour is suddenly formed
under the right ear; swallowing is rendered difficult and painful; and
the patient refuses all food and medicine. Nourishing clysters are
directed; but it is to be feared that these will renew the looseness,
and that this amiable youth will quickly sink under his disorder[22].

The use of _wort_ from its saccharine quality, and disposition to
ferment, has lately been proposed as a remedy for the SEA SCURVY. Water
or other liquors, already abounding with fixed air in a separate state,
should seem to be better adapted to this purpose; as they will more
quickly correct the putrid disposition of the fluids, and at the same
time, by their gentle stimulus[23] increase the powers of digestion, and
give new strength to the whole system.

Dr. Priestley, who suggested both the idea and the means of executing
it, has under the sanction of the College of Physicians, proposed the
scheme to the Lords of the Admiralty, who have ordered trial to be made
of it, on board some of his Majesty's ships of war. Might it not however
give additional efficacy to this remedy, if instead of simple water, the
infusion of malt were to be employed?

I am persuaded such a medicinal drink might be prescribed also with
great advantage in SCROPHULOUS COMPLAINTS, when not attended with a
hectic fever; and in other disorders in which a general acrimony
prevails, and the crasis of the blood is destroyed. Under such
circumstances, I have seen _vibices_ which spread over the body,
disappear in a few days from the use of wort.

A gentleman who is subject to a scorbutic eruption in his face, for
which he has used a variety of remedies with no very beneficial effect,
has lately applied the fumes of chalk and oil of vitriol to the parts
affected. The operation occasions great itching and pricking in the
skin, and some degree of drowsiness, but evidently abates the serous
discharge, and diminishes the eruption. This patient has several
symptoms which indicate a genuine scorbutic DIATHESIS; and it is
probable that fixed air, taken internally, would be an useful medicine
in this case.

The saline draughts of Riverius are supposed to owe their antiemetic
effects to the air, which is separated from the salt of wormwood during
the act of effervescence. And the tonic powers of many mineral waters
seem to depend on this principle. I was lately desired to visit a lady
who had most severe convulsive REACHINGS. Various remedies had been
administered without effect, before I saw her. She earnestly desired a
draught of malt liquor, and was indulged with half a pint of Burton beer
in brisk effervescence. The vomitings ceased immediately, and returned
no more. Fermenting liquors, it is well known, abound with fixed air. To
this, and to the cordial quality of the beer, the favourable effect
which it produced, may justly be ascribed. But I shall exceed my design
by enlarging further on this subject. What has been advanced it is
hoped, will suffice to excite the attention of physicians to a remedy
which is capable of being applied to so many important medicinal
purposes.

NUMBER IV.

_Extract of a Letter from WILLIAM FALCONER, M.D. of BATH._

                                      Jan 6, 1774,

     Reverend Sir,

I once observed the same taste you mention (Philosophical Transactions,
p. 156. of this Volume, p. 35.) viz. like tar water, in some water that
I impregnated with fixed air about three years ago. I did not then know
to what to attribute it, but your experiment seems to clear it up. I
happened to have spent all my acid for raising effervescence, and to
supply its place I used a bottle of dulcified spirit of nitre, which I
knew was greatly under-saturated with spirit of wine; from which, as
analogous to your observation, I imagine the effect proceeded.

As[24] to the coagulation of the blood of animals by fixed Air, I fear
it will scarce stand the test of experiment, as I this day gave it, I
think, a fair trial, in the following manner.

A young healthy man, at 20 years old, received a contusion by a fall,
was instantly carried to a neighbouring surgeon, and, at my request,
bled in the following manner.

I inserted a glass funnel into the neck of a large clear phial about oz.
x. contents, and bled him into it to about oz. viii. By these means the
blood was exposed to the air as little a time as possible, as it flowed
into the bottle as it came from the orifice.

As soon as the quantity proposed was drawn, the bottle was carefully
corked, and brought to me. It was then quite fluid, nor was there the
least separation of its parts.

On the surface of this I conveyed several streams of fixed air (having
first placed the bottle with the blood in a bowl of water, heated as
nearly to the human heat as possible) from the mixture of the vitriolic
acid and lixiv. tartar, which I use preferably to other alkalines, as
being (as Dr. Cullen observes) in the mildest state, and therefore most
likely to generate most air.

I shook the phial often, and threw many streams of air on the blood, as
I have often practised with success for impregnating water; but could
not perceive the smallest signs of coagulation, although it stood in an
atmosphere of fixed air 20 minutes or more. I then uncorked the bottles,
and poured off about oz. ii to which I added about 6 or 7 gtts of spirit
of vitriol, which coagulated it immediately. I set the remainder in a
cold place and it coagulated, as near as I could judge, in the same time
that blood would have done newly drawn from the vein.

P. 82. Perhaps the circumilance of putrid vegetables yielding all fixed
and no inflammable air may be the causes of their proving so antiseptic,
even when putrid, as appears by Mr. Alexander's Experiments.

P. 86. Perhaps the putrid air continually exhaled may be one cause of
the luxuriancy of plants growing on dunghills or in very rich soils.

P. 146. Your observation that inflammable air consists of the union of
some acid vapour with phlogiston, puts me in mind of an old observation
of Dr. Cullen, that the oil separated from soap by an acid was much more
inflammable than before, resembling essential oil, and soluble in V. sp.

I have tried fixed air as an antiseptic taken in by respiration, but
with no great success. In one case it seemed to be of service, in two it
seemed indifferent, and in one was injurious, by exciting a cough.

NUMBER V.

_Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT MASSINGHAM,
NORFOLK._

                                      March 23, 1774.

     Dear Sir,

When I first received your paper, I happened to have a process going on
for the preparation of _nitrous ether_, without distillation.[25] I had
heretofore always taken for granted that the elastic fluid generated in
that preparation was _fixed_ air: but on examination I found this
combination of the nitrous acid with inflammable spirits, produced an
elastic fluid that had the same general properties with the air that you
unwillingly, though very properly, in my opinion, term _nitrous_; as I
believe it is not to be procured without employing the _nitrous_ acid,
either in a simple state, or compounded, as in _aqua regia_. I shall
suggest, however, by and by some doubts with respect to it's title to
the appellation of _air_.

Water impregnated with your nitrous air _certainly_, as you suspected
from it's taste, contains the nitrous acid. On saturating a quantity of
this water with a fixed alcali, and then evaporating, &c. I have
procured two chrystals of nitre. But the principal observations that
have occurred to me on the subject of nitrous air are the following. My
experiments have been few and made by snatches, under every disadvantage
as to apparatus, &c. and with frequent interruptions; and yet I think
they are to be depended upon.

My first remark is, that nitrous air does not give water a sensibly acid
impregnation, unless it comes into contact, or is mixed with a portion
of common or atmospherical air: and my second, that nitrous air
principally consists of the nitrous acid itself, reduced to the state of
a _permanent_ vapour not condensable by cold, like other vapours, but
which requires the presence and admixture of common air to restore it to
its primitive state of a liquid. I am beholden for this idea, you will
perceive, to your own very curious discovery of the true nature of Mr.
Cavendish's _marine_ vapour.

When I first repeated your experiment of impregnating water with nitrous
air, the water, I must own tasted acid; as it did in one, or perhaps two
trials afterwards; but, to my great astonishment, in all the following
experiments, though some part of the factitious air, or vapour, was
visibly absorbed by the water, I could not perceive the latter to have
acquired any sensible acidity. I at length found, however, that I could
render this same water _very_ acid, by means only of the nitrous air
already included in the phial with it. Taking the inverted phial out of
the water, I remove my finger from the mouth of it, to admit a little
of the common air, and instantly replace my finger. The redness,
effervescence, and diminution take place. Again taking off my finger,
and instantly replacing it, more common, air rushes in, and the same
phenomena recur. The process sometimes requires to be seven or eight
times repeated, before the whole of the nitrous _vapour_ (as I shall
venture to call it) is condensed into nitrous _acid_, by the successive
entrance of fresh parcels of common air after each effervescence; and
the water becomes evidently more and more acid after every such fresh
admission of the external air, which at length ceases to enter, when the
whole of the vapour has been condensed. No agitation of the water is
requisite, except a gentle motion, just sufficient to rince the sides of
the phial, in order to wash off the condensed vapour.

The acidity which you (and I likewise, at first) observed in the water
agitated with nitrous air _alone_, I account for thus. On bringing the
phial to the mouth, the common air meeting with the nitrous vapour in
the neck of the phial, condenses it, and impregnates the water with the
acid, in the very act of receiving it upon the tongue. On stopping the
mouth of the phial with my tongue for a short time and afterwards
withdrawing it a very little, to suffer the common air to rush past it
into the phial, the sensation of acidity has been sometimes intolerable:
but taking a large gulph of the water at the same time, it has been
found very slightly acid.--The following is one of the methods by which
I have given water a very strong acid impregnation, by means of a
mixture of nitrous and common air.

Into a small phial, containing only common air, I force a quantity of
nitrous air at random, out of a bladder, and instantly clap my finger on
the mouth of the bottle. I then immerse the neck of it into water, a
small quantity of which I suffer to enter, which squirts into it with
violence; and immediately replacing my finger, remove the phial. The
water contained in it is already _very_ acid, and it becomes more and
more so (if a sufficient quantity of nitrous air was at first thrown in)
on alternately stopping the mouth of the phial, and opening it, as often
as fresh air will enter.

Since I wrote the above, I have frequently converted a small portion of
water in an ounce phial into a weak _Aqua fortis_, by repeated mixtures
of common and nitrous air; throwing in alternately the one or the other,
according to the circumstances; that is, as long as there was a
superabundance of nitrous air, suffering the common air to enter and
condense it; and, when that was effected, forcing in more nitrous air
from the bladder, to the common air which now predominated in the
phial--and so alternately. I have wanted leisure, and conveniences, to
carry on this process to its _maximum_, or to execute it in a different
and better manner; but from what I have done, I think we may conclude
that nitrous air consists principally of the nitrous acid,
phlogisticated, or otherwise so modified, by a previous commenstruation
with metals, inflammable spirits, &c. as to be reduced into a durably
elastic vapour: and that, in order to deprive it of its elasticity, and
restore it to its former state, an addition of common air is requisite,
and, as I suspect, of water likewise, or some other fluid: as in the
course of my few trials, I have not yet been able to condense it in a
perfectly dry bottle.

NUMBER VI.

_A Letter from_ Dr. FRANKLIN.

                              Craven Street, April 10, 1774.

     Dear Sir,

In compliance with your request, I have endeavoured to recollect the
circumstances of the American experiments I formerly mentioned to you,
of raising a flame on the surface of some waters there.

When I passed through New Jersey in 1764, I heard it several times
mentioned, that by applying a lighted candle near the surface of some of
their rivers, a sudden flame Would catch and spread on the water,
continuing to burn for near half a minute. But the accounts I received
were so imperfect that I could form no guess at the cause of such an
effect, and rather doubted the truth of it. I had no opportunity of
seeing the experiment; but calling to see a friend who happened to be
just returned home from making it himself, I learned from him the manner
of it; which was to choose a shallow place, where the bottom could be
reached by a walking-stick, and was muddy; the mud was first to be
stirred with the stick, and when a number of small bubbles began to
arise from it, the candle was applied. The flame was so sudden and so
strong, that it catched his ruffle and spoiled it, as I saw. New-Jersey
having many pine-trees in different parts of it, I then imagined that
something like a volatile oil of turpentine might be mixed with the
waters from a pine-swamp, but this supposition did not quite satisfy me.
I mentioned the fact to some philosophical friends on my return to
England, but it was not much attended to. I suppose I was thought a
little too credulous.

In 1765, the Reverend Dr. Chandler received a letter from Dr. Finley,
President of the College in that province, relating the same experiment.
It was read at the Royal Society, Nov. 21, of that year, but not printed
in the Transactions; perhaps because it was thought too strange to be
true, and some ridicule might be apprehended if any member should
attempt to repeat it in order to ascertain or refute it. The following
is a copy of that account.

"A worthy gentleman, who lives at a few miles distance, informed me that
in a certain small cove of a mill-pond, near his house, he was surprized
to see the surface of the water blaze like inflamed spirits. I soon
after went to the place, and made the experiment with the same success.
The bottom of the creek was muddy, and when stirred up, so as to cause a
considerable curl on the surface, and a lighted candle held within two
or three inches of it, the whole surface was in a blaze, as instantly as
the vapour of warm inflammable spirits, and continued, when strongly
agitated, for the space of several seconds. It was at first imagined to
be peculiar to that place; but upon trial it was soon found, that such a
bottom in other places exhibited the same phenomenon. The discovery was
accidentally made by one belonging to the mill."

I have tried the experiment twice here in England, but without success.
The first was in a slow running water with a muddy bottom. The second in
a stagnant water at the bottom of a deep ditch. Being some time employed
in stirring this water, I ascribed an intermitting fever, which seized
me a few days after, to my breathing too much of that foul air which I
stirred up from the bottom, and which I could not avoid while I stooped
in endeavouring to kindle it.--The discoveries you have lately made of
the manner in which inflammable air is in some cases produced, may throw
light on this experiment, and explain its succeeding in some cases, and
not in others. With the highest esteem and respect,

     I am, Dear Sir,

       Your most obedient humble servant,

         B. FRANKLIN.

NUMBER VII.

_Extract of a Letter from_ Mr. HENRY _of_ Manchester.

It is with great pleasure I hear of your intended publication _on air_,
and I beg leave to communicate to you an experiment or two which I
lately made.

Dr. Percival had tried, without effect, to dissolve lead in water
impregnated with fixed air. I however thought it probable, that the
experiment might succeed with nitrous air. Into a quantity of water
impregnated with it, I put several pieces of sheet-lead, and suffered
them, after agitation, to continue immersed about two hours. A few drops
of vol. tincture of sulphur changed the water to a deep orange colour,
but not so deep as when the same tincture was added to a glass of the
same water, into which one drop of a solution of sugar of lead had been
instilled. The precipitates of both in the morning, were exactly of the
same kind; and the water in which the lead had been infused all night,
being again tried by the same test, gave signs of a still stronger
saturnine impregnation--Whether the nitrous air acts as an acid on the
lead, or in the same manner that fixed air dissolves iron, I do not
pretend to determine. Syrup of violets added to the nitrous water became
of a pale red, but on standing about an hour, grew of a turbid brown
cast.

Though the nitrous acid is not often found, except produced by art, yet
as there is a probability that nitre may be formed in the earth in large
towns, and indeed fossile nitre has been actually found in such
situations, it should be an additional caution against the use of leaden
pumps.

I tried to dissolve mercury by the same means, but without success.

     I am, with the most sincere esteem,

       Dear Sir,

         Your obliged and obedient servant,

           THO. HENRY.

_FINIS._

FOOTNOTES:

[15] See Dr. Falconer's very useful and ingenious treatise on the Bath
water, 2d edit. p. 313.

[16] May, 1772.

[17] Vid. Mr. White's useful treatise on the management of pregnant and
lying-in women, p. 279.

[18] See the author's observations on the efficacy of external
applications in the ulcerous sore throats, Essays medical and
experimental, Vol. I. 2d edit. p. 377.

[19] The author of these observations.

[20] Directions for impregnating water with fixed air, in order to
communicate to it the peculiar spirit and virtues of Pyrmont water, and
other mineral waters of a similar nature.

[21] Referring to the case communicated by Mr. Hey.

[22] He languished about a week, and then died.

[23] The vegetables which are most efficacious in the cure of the
scurvy, possess some degree of a stimulating power.

[24] This refers, to an experiment mentioned in the first publication of
these papers in the Philosophical Transactions, but omitted in this
volume.

[25] The first account of this curious process was, I believe, given in
the Mem. de l'Ac. de Sc. de Paris for 1742. Though seemingly less
volatile than the vitriolic ether, it boils with a much smaller degree
of heat. One day last summer, it boiled in the coolest room of my house;
as it gave me notice by the explosion attending its driving out the
cork. To save the bottle, and to prevent the total loss of the liquor by
evaporation, I found myself obliged instantly to carry it down to my
cellar.

ERRATA.

     P. 15. l. 13.  _for_  it to  _read_  to it

     p. 24. l. 20.    ----       has      ----      had

     p. 60. l. 22.    ----     inflammable ----     in inflammable

     p. 84. l. 5.     ----     experiments ----     experiment

     p. 145. l. 16.   ----     with        ----     of

     p. 153. l. 1.    ----     that is     ----     this air

     p. 199. l. 17.   ----     ingenious   ----     ingenuous

     p. 211. l. 23.   ----     of          ----     , if

     p. 243. l. 27.   ----     diminishing ----     diminished

     p. 272. l. 21.   ----     seem        ----     seems

     p. 301. l. 31.   ----     ----        ----     one end

     p. 303. l. 5.    ----     ----        ----     the nitrous

     p. 304. l. 21.   ----     deslrium    ----     delirium

     p. 306. l. 2.    ----     recet.      ----     recent.

     p. 308. l. 7.    ----     per         ----     Peruv.

     p. 313. l. 27.   ----     usual       ----     useful

     p. 300. to 314.  passim   ----        Diarrhæa ---- Diarrhoea

     p. 316. l. 11.   ----     remains     ----     remainder

     p. 524. l. 15.   ----     it          ----     iron.

A CATALOGUE of BOOKS written by

JOSEPH PRIESTLEY, LL.D. F.R.S.,

_And printed for_

J. JOHNSON, BOOKSELLER, at No. 72,

St. Paul's Church-Yard, London.

1. The HISTORY and PRESENT STATE of ELECTRICITY, with original
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enlarged, 4to. 1l. 1s.

2. A FAMILIAR INTRODUCTION to the STUDY of ELECTRICITY, 2d Edit. 8vo.
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_Also, published under the Direction of Dr. PRIESTLEY_,

THE THEOLOGICAL REPOSITORY.

    Consisting of original Essays, Hints, Queries, &c. calculated to
    promote religious Knowledge, in 3 Volumes, 8vo, Price 18s. in
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Among other Articles, too many to be enumerated in an Advertisement,
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[Illustration: _To face the last page._]