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and fublimed from it about two or three grains of yellow fulphur. This fulphur, which ftuck to the neck of the retort, when opened, had an oily appearance; and the retort, when opened, had not only the smell of the volatile fulphureous acid, which ufually accompanies the fublimation of fulphur, but it had alfo the strong empyreumatic smell which peculiarly appertains to burnt oils; and it retained the fmell for feveral days. It has been remarked before, that the falt feparable from the fulphur water was of a brownish colour; and others, who have analyfed this water, have met with a brown fubftance, which they knew not what to make of; both which appear ances may be attributed to the oil, the existence of which was rendered fo manifeft by the fublimation here mentioned. I will not trouble the Society with any conjectures concerning the origin of this oil, or the medium of its combination with water; the difcovery of it gave me fome pleafure, as it feemed to add a degree of probability to what I had faid concerning the nature of the air with which, in one of my Chemical Effays, I had fuppofed Harrogate water to be impregnated. I will again take the liberty of repeating the query which I there propofed. "Does this air, and the inflammable air feparable from fome metallic fubftances, confift of oleaginous particles in an elaftic ftate?" When I ventured to conjecture, in the effay alluded to, that fulphureous waters received their impregnation from air of a particular kind, I did not know that profeffor Bergman had advanced the fame opinion, and denominated that fpecies of air, Hepatic-air. I have fince then feen his works, and very readily give up to him not

only the priority of the discovery, but the merit of profecuting it. And though what he has faid concerning the manner of precipitating fulphur from these waters can leave no doubt in the mind of any chemift concerning the actual existence of fulphur in them; yet I will proceed to mention fome other obvi ous experiments on the Harrogate water, in fupport of the fame doc trine.

"Knowing that, in the baths of Aix-la-Chapelle, fulphur is found sticking to the fides and top of the channel in which the fulphureous water is conveyed, I examined with great attention the fides of the little ftone building which is raised over the bafon of the ftrongest well, and faw them in fome places of a yellowish colour: this I thought proceeded from a fpecies of yellow mofs, commonly found on grit ftone: I collected, however, what I could of it by brufhing the fides of the building, at the diftance of three or four feet from the water in the bafon: on putting what I had brushed off on a hot iron, I found that it confifted principally of particles of grit-stone, evidently however mixed with particles of fulphur.

"Much of the fulphureous wa ter is ufed for baths at Harrogate ; and for that purpose all the four wells are frequently emptied into large tubs containing many gallons apiece; thefe conftantly ftand at the wells; and the cafks, in which the water is carried to the feveral houfes, are filled from them. On examining the infides of these tubs, I found them covered, as if painted, with a whitish pellicle. fcraped off a part of this pellicle: it was no longer foluble in water; but, being put on a hot iron, it appeared to confift almost wholly

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of fulphur. Some of these tubs
have been in ufe many years, and
the adhering cruft is thick in pro-
portion to the time they have been
applied to the purpofe; but the
fulphur pellicle was fufficiently
obfervable on one which was new
in the beginning of this feafon.
The water when it is first put into
thefe tubs is tranfparent; when it
has been expofed to the air for a
few hours, it becomes milky; and,
where the quantity is large, a
white cloud may be feen flowly
precipitating itfelf to the bottom:
this white precipitate confifts partly,
I am not certain that it confifts
wholly, of fulphur; and the ful-
phur is as really contained in the
waters denominated fulphureous,
as iron is contained in certain forts
of chalybeate waters; in the one
cafe the iron is rendered foluble
in water by its being united to fixed
air, or fome other volatile princi-
ple; and in the other fulphur is
rendered foluble in water by its
being united to fixed air, or fome
other volatile principle: neither
iron nor fulphur are of themselves
foluble in water, but each of them,
being reduced into the form of a
falt by an union with fome other
fubstances, becomes foluble in wa-
ter, and remains diffolved in it, till
that other fubitance either efcapes
into the air, or becomes combined
with fome other body.

"About forty years ago, they
took up the bason of the third well,
and a credible perfon, who was
himfelf prefent at the operation
informed me, that in all the cre-
vices of the flone on which the
bafon refted, there were layers of
Pure yellow fulphur. This I can
well believe, for I ordered a piece of
fhale to be broken off from he bottom
of the fourth well; it was split,
as hale generally is into feveral

thin pieces, and was covered with a whitish cruft. But laid on a hot iron, in a dark room, it crackled very much, and exhibited a blue flame and fulphureous smell.

"If the water happens to ftand a few days in any of the wells, without being disturbed, there is found at the bottom a black sediment; this black fediment alfo marks the courfe of the water which flows from the well, and it may be efteemed characteristic of a fulphur water. The furface of the water alfo, when it is not stirred for fome time, is covered with a whitish. feum. Dr. Short had long ago obferved, that both the black fediment, and the white fcum, gave clear indications on a hot iron, of their containing fulphur: I know not whence it has come that his accuracy has been questioned in this point; certain I am, that on the repetition of his experiments I found them true. The white fcum alfo, which is found flicking on the grafs over which the water flows, being gently dried, burns with the flame and smell of fulphur. From what has been faid it is clear, that fulphur is found at Harrogate, flicking to the bafon into which the water fprings; fublimed upon the ftones which compofe the edifice furrounding the well; adhering to the fides of the tubs in which the water ftands; fubfiding to the bottom of the channel in which the water runs; and covering the furface of the earth, and of the blades of grafs, over which it flows. It is unneceffary to add another word on this fubject; it remains that I risk a conjecture or two, on the primary caufe of the fulphureous impregnation obfervable in these waters.

"In the Chemical Effay before referred to, I have fhewn, that the

the

air feparable from the lead ore of Derbyshire, or from Black-Jack, by folution in the acid of vitriol, impregnates common water with the fulphurcous finell of Harrogate water; and I have alfo fhewn that the bladder fucus or fea-wrack, by being calcined to a certain point, and put into water, not only gives the water a brackish tafle, but communicates to it, without injuring its tranfparency, the fmell, tafte, and other properties of Harrogate water. Profeffor Bergman impregnated water with a fulphureous tafle and finell, by means of air feparated by the vitriolic acid from hepar fulphuris, made by fufion of equal weights of fulphur and pot-afhes, and from a mafs made of three parts of iron filings melted with two of fulphur; and he found alfo, that Black-Jack and native Siberian iron yielded hepatic air, by folution in acids. This, I believe, is the main of what is known by chemias on this fubject; what I have to fuggeft, relative to the Harrogate waters in particular, may perhaps be of ufe to future enquires.

"I have been told, that on breaking into an old coal-work, in which a confiderable quantity of wood had been left rotting for a long time, there iflued out a great quantity of water finelling like Harrogate water, and leaving, as that water does, a white fcum on the cath over which it paffed. On opening a well of common water, in which there was found a log of rotten wood, an obfervant phyfician affured me, that he had perceived a frong and diftinct fmell of Harrogate water. Dr. Darwin, in his ingenious account of an Artificial Spring of Water, publifhed in the first part of the LXXVth. Volume of the Philofophical Tranf

actions, mentions his having per ceived a flight fulphureous fmell and tafte in the water of a well which had been funk in a black, loofe, moift earth, which appeared to have been very lately a morafs, but which is now covered with houfes built upon piles. In the bog or morals above mentioned there is great plenty of fulphureous water which feems to fpr ng from the earth of the rotten wood of which that bog confifts. Thefe facts are not fufficient to make us certain, that rotten wood is effcacious in impregnating water with a fulphureous finell; because there are many bogs in every part of the world, in which no fulphureous water has ever been difcovered. Nor, on the other hand, are they to be rejected as of no ufe in the inquiry; becaufe wood, at a particular period of its putrefaction, or when fituated at a particular depth, or when incumbent on a foil of a particular kind, may give an impregnation to water, which the fame wood, under different circumftances, would not give.

"The bilge water, ufually found at the bottom of fhips which are foul, is faid to fmell like Harrogate water: 1 at first fuppofed, that it had acquired this fmeil in confequence of becoming putrid in contact with the timber on which it refed, and this circumftance I confidered as a notable fupport to the conjecture I had formed of rot-. ten wood, being under certain circumftances, inftrumental in generating the fmell of Harrogate wa ter. But this notion is not well founded; for the bilge water is, I fuppofe, falt water; and Dr. Short fays that fea water, which had been kept in a ftone bottle fix weeks "ftunk not much fhort of Harrogate fulphur water." It has been remarked

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temarked above, that calcined fea wrack, which contains a great deal of fea falt, exhales an odour fimilar in all refpects to that of Harrogate water; and in confirmation of the truth of this remark, I find that an author, quoted by Dr. Short, fays, that "Bay falt thrice calcined, diffolved in water, gives exactly the odour of the fulphur well at Harrogate." From thefe experiments confidered together, it may, perhaps, be inferred, that common falt communicates a fulphureous fmell to water both by putrefaction and calcination. Hence fome may think, that there is fome probability in the fuppofition, that either a calcined ftratum of common falt, or a putrefcent falt fpring may contribute to the production of the fulphurcous fmell of Harrogate water; efpecially as thefe wa ters are largely impregnated with common falt. However, as neither the falt in fea-water, nor that of calcined fea-wrack, nor calcined bay falt, are any of them abfolute ly free from the admixture of bodies containing the vitriolic acid, a doubt till remains, whether the fulphureous exhalation, here fpoken of, can be generated from fubftances in which the vitriolic acid does not exist.

"The fhale from which alum is made, when it is firit dug out of the earth, gives no impregnation to water; but by expofure to air and moilure its principles are loofened, it fhivers into pieces, and finally moulders into a kind of clay, which has an aluminous tafte. Alum is an earthy falt, refulting from an nion of the acid of fulphur with pure clay; and hence we are fure, that fhale, when decompofed by the air, contains the acid of fulphur; and from its oily black appearance, and efpecially from its being in1786.

flammable, we are equally certain that it contains plogiton, the other conftituent part of fulphur. And indeed, pyritous fubftances, or com binations of fulphur and iron, enter into the composition of many, probably of all forts of fhale, though the particles of the pyrites may not be large enough to be feen in fome of them; and if this be admitted, then we need be at no lofs to account for the bits of fulphur, which are fublimed to the top of the heaps of fhale, when they calcine large quantities of it for the purpose of making alum: nor need we have any difficulty in admitting, that a phlogidic vapour must be difcharged from fhale, when it is decompofed by the air. Dr. Short fays, that he burned a piece of aluminous fhale for half an hour in an open fire; he then powdered and infufed it in common water, and the water fent forth a moit intolerable fulphureous fmell, the very fame with Harrogate water. He burned several other peces of fhale, but none of them ftunk fo ftrong as the first.` This difference may be attributed either to the different qualities of the different pieces of fhale which he tried, or to the calcination of the first being pushed to a certain definite degree; for the combina. tion of the principles on which the fmell depends may be produced by one degree of heat, and deftroyed by another. I have mentioned, briefly, thefe properties of fhale, becaufe there is a tratum of fhale extended over all the country in the neighbourhood of Harrogate; feveral beds of it may be feen in the ftone quarry above the fulphur wells; many of the brooks about Harrogate run upon fhale, and the fulphur wells fpring out of it. They have bored to the depth of twenty yards into this fhale, in different

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places,

places, in fearch of coal, but have have never penetrated through it. Its hardness is not the fame at all depths. Some of it will strike fire, as a pyrites does with fteel; and other beds of it are foft, and in a ftate of decompofition, and the fulphur water is thought to rife out of that fhale which is in the fofteft ftate. But whatever impregnation fhale when calcined, or otherwife decomposed to a particular degree, may give to the water which paffes over it, it must not be concluded, that fhale in general gives water a fulphurcous impregnation; fince there are many fprings, in various parts of England, arifing out of fhale, in which no fuch impregnation is obferved.

"I forgot to mention in its proper place, that having vifited the bog, fo often spoken of, after a long feries of very dry weather, I found its furface, where there was no grafs, quite candied over with a yellowish cruft, of tolerable confiflency, which had a strong aluminous tale, and the fmell of honey.

Bergman fpeaks of a turf found at Helfingberg, in Scania, confifting of the roots of vegetables, which was often covered with a pyritous cuticle, which, when elixated, yielded alum; and I make no doubt, that the Harrogate morafs is of the fame kind.

"Whether nature ufes any of the methods which I have mentioned of producing the air by which fulphureous waters are impregnated, may be much queftioned; it is of ufe, however, to record the experi ments by which her productions may be imitated; for though the line of human understanding will never fathom the depths of divine wifdom, difplayed in the formation of this little globe which we inhabit; yet the impulfe of attempting an investigation of the works of God is irrefiftible; and every phyfical truth which we difcover, every little approach which we make towards a comprehenfion of the mode of his operation, gives to a mind of any piety the most pure and sublime fatisfaction."

The Prefent State of MOUNT VESUVIUS; with the Account of a Voyage to the Ifland of PONZA. In a Letter from Sir WILLIAM HAMILTON, K. B. F. R. S. to Sir JOSEPH BANKS, Bart. P. R.S.

ΤΗ

[From the fame Publication. ]

HE eruption of Mount Vefuvius, which began in the month of November, 1784, nearly at the moment of my return from England to this capital, and which continued in fome degree till about the 2cth of last month has afforded much amufement to travellers unacquainted with this won

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