Philosophical transactions, Vol. L. Part I. For the year 1757. · Various
II.
No coins of any sort have been found in the peat. But there may, perhaps, be a variety of things at the bottom of it: but as the peat is always full of water, which is never quite drained off, so it is not an easy matter to examine the bottom. I beg leave to assure you, my Lord, that I am, with great respect and esteem, Your Lordship’s most obliged, and obedient humble Servant, John Collet. XVI. _An Account of the Alterations making in the_ Pantheon _at_ Rome: _In an Extract of a Letter from_ Rome _to_ Thomas Hollis, _Esq; Communicated by_ John Ward, _LL.D. R.S. Vice-Præs._ [Read Mar. 3, 1757.] A Project was lately laid before the government by Paolo Posi, an architect, for modernizing the inside of the Pantheon, and unfortunately approved. In consequence of which, the dome has been already cleaned, and rough cast; and the remainder of the lead taken away, which served as a lining to the silver work, that originally covered it. The vestiges of the cornices, and other ornaments of the silver work, were still discernible in the lead, which was fastened by very large iron nails. All this was effected by a moveable scaffold, that was fixed to the bronze cornice of the open circle above, whereby the temple is illuminated, and descended to the cornice of the Attic order, being as curious in the contrivance, as detestable for the purposes intended by it. It is true, we could not before see the dome in its pristine glory; but we had the satisfaction of viewing the traces and remains of what it had been. Nor could the adepts in architecture sufficiently admire the skill and sagacity of the builder, who, composing it of a number of small arches, which together formed a kind of net-work, and filling up the intervals between with pumice-stones and mortar, gave it that strength and lightness, whereby it has probably stood so many ages.
The evil would be comparatively small, had the project extended no farther, than what has been related; but they are now busy in removing the Attic order, to make room for a new invention, suitable to the trifling taste, which at this day prevails. And not content with that, they think of taking away the ancient pavement; and, what is still worse, its peculiar beauty, the open circle at the top, to place a lanthorn instead of it, as is usual in modern cupola’s. You had the good fortune, Sir, to view this remarkable temple, in that state, wherein it was left by the ancient barbarians: but those, who see it hereafter, will find it in a much more deplorable condition, stripped of its precious marbles and ornaments; and so disguised by modern alterations, that the noble form given it by Agrippa will be no longer distinguishable. It is said Il Signor J.B. Piranesi, the architect, who published the antiquities of Rome, and divers ingenious works of that kind, has taken accurate plans of the Attic order, and every other particular relating to it. These he proposes to engrave and publish, with exact explanations annexed to them; together with a plan of the whole, as he believes it appeared in its original splendor and perfection; that posterity may not be deprived of informations, which are of so great benefit and importance to all lovers of architecture. It is also said, that the engineer [carpenter], who invented the scaffolding, has made an exact model of it for him; which he intends to publish as a part of the work before-mentioned.
XVII. _An Account of a new medicinal Well, lately discovered near_ Moffat, _in_ Annandale, _in the County of_ Dumfries. _By Mr._ John Walker, _of_ Borgue-House, _near_ Kirkudbright, _in_ Scotland. [Read Feb. 10, & Mar. 3, 1757.] THIS mineral spring was found out by one Mr Williamson, a few years ago, when he was overseeing a mine, which was at that time carrying on in its neighbourhood. It is situate about four miles distant from Moffat, in the bottom of a deep scar, which is on the west side of a large mountain called Hartfell, from which it has acquired the name of Hartfell-spaw. This scar is a part of the mountain, thro’ which a small stream of water has worn its way to a considerable depth; by which it has laid open, and exposed to view, the strata of the earth on each side: and in the bottom of this scar, and near to the brink of this small brook, the mineral water springs up.
When I saw it, it consisted of two springs, which were very well ordered by Mr. Williamson, so as to run from two wooden spouts, immediately at their rise out of the earth; which indeed must be of very great advantage to all mineral waters; and I am persuaded there are many, whose medical qualities are greatly impaired by falling into reservoirs, and continuing in them for some time after they spring from the earth. The one of these springs was situate about ten or twelve yards farther up the brook than the other; and they were then distinguished by the names of the upper and lower spring: but I have been since informed, that their situation is now altered. Each of these springs did at that time run nearly the same quantity of water, which, as I thought, was above an English quart in a minute, and that during a season of very dry weather. As there are many instances of mineral waters springing out of the earth very near each other, which at the same time are impregnated with very different principles; it therefore seemed not at all improbable, that as these waters did appear to run, for some part of their course, in different channels, they might in some respects be different from each other. And this suspicion I found not to be altogether groundless with regard to these springs, as will be shewn afterwards. For which reason it may be observed, that the following trials were all made upon the water of the upper fountain, except where the other is particularly mentioned; and also that they were made within 24 hours after the water was taken from the spring, being carried to Moffat in bottles carefully sealed.
According to what may be inferred from the following experiments, it may be premised, that this water appears to contain in it a large proportion of iron, but in two different forms; and an aluminous salt, which is conjoined with a terrestrial principle. As the contents of several mineral waters have been the cause of many different opinions, and of great disputes among physicians and chymists; as the inquiry I made into the principles of these waters, which I am now considering, was not performed with that nicety and exactness I could have wished; and as I am persuaded, that to dogmatize in any branch of philosophy can never tend to its advancement; I shall not therefore pretend to determine with certainty in any part of this subject, where the contrary opinion can be admitted with the least degree of probability. These trials are indeed but few and imperfect, and are no-way sufficient to form an exact account of this mineral water; yet I believe they may afford some conclusions, which may be serviceable in compiling a more compleat history of it. They render it pretty evident, that the above-mentioned principles are contained in these waters: and tho’ I will not pretend absolutely to exclude all others, yet I must say, that, by what inquiry I made, I could not observe them to be in the least impregnated with any other kind of mineral substance.
After a good deal of observation upon the water of this Spaw; and after many fruitless attempts, which I have at different times made upon several other waters of the chalybeat kind in Scotland, in quest of the volatile spirit, which has been commonly attributed to them; I must own, that I have been induced to think, that there is no such thing exists in these waters at all. What has been generally called the spirit of steel waters, seems to me to be very unintelligible; altho’ the existence of it in these waters has been asserted by all the writers on this subject, which I have yet had occasion to see. The spirit of a mixed body is commonly taken to be a subtile, penetrating, light, and volatile substance, more susceptible of motion than any other of its parts, and most easily separable from them by avolation. But that any chalybeat water contains such a substance, I think has never been made evident, unless where the water has been found to be impregnated with some other mineral principles. Some steel waters, I believe, contain a large proportion of air, whose elasticity may occasion it to break forth with an explosive force; some others there are, which contain a volatile and sulphureous halitus; and to one or other of these two causes, or to some other mineral principle, I think most of the phænomena may be referred, which have been attributed to a ferrugineous or vitriolic volatile spirit.
As the first thing observable in a mineral water is its outward form, we must therefore take notice, that the water of this Spaw equals the clearest spring-water in transparency; and is likewise as free of any colour or odour: yet its taste is very strong, and may be discerned to be compounded of a sweet, subacid, and astringent taste. Its sweetness and acidity appear sensibly to arise from alum; and its high styptic and astringent taste does as evidently proceed from that mineral salt, joined with some earthy or ferrugineous parts. I must likewise observe, that when I first compared the taste of these two springs, I could plainly discern, that the water of the lower spring was more acid, and less astringent, than that of the upper one; and, on the contrary, the water of the upper spring seemed more astringent, and less acid. This induced me to think, that the mineral parts, which caused the acid and astringent tastes, were mixed in the waters of these two springs in different proportions. And what I observed of them afterwards still confirmed this conjecture. But, in order to give some evidence for the existence of the above-mentioned minerals in the waters of these springs, we shall consider them separately, by relating the experiments, which seemed to indicate, that they are contained in these waters in a very considerable proportion, and by offering some conclusions, which may be reasonably drawn from them.
And as the first trials were made in quest of iron, it may perhaps be most proper to consider it in the first place. _Experiment_ 1. Some pieces of galls being added to equal quantities of the water of the two springs, an exceeding deep and bright blue colour was immediately produced in the water of the upper spring, which in a little time turned to a perfect black. The water of the lower spring, tho’ indeed it was turned of the same colour, yet was not of so deep a shade, but was somewhat lighter than the former. The tincture of galls caused the same appearances. 2. A tincture of balaustine-flowers produced the above blue colours in both waters. 3. A quantity of the water being thoroughly tinged with galls, was allowed to stand 24 hours: being then filtrated thro’ brown paper, the water, tho’ almost quite colourless, would not again receive any tincture with galls. 4. After elixation the water became of a turbid yellow colour with ochre, and afforded very little tincture with galls. 5. A solution of sal Martis, chemically prepared, being mixed with galls, immediately turned of a bright dark blue colour, exactly similar to that produced in the water. 6. A solution of common and rock alum was no-ways changed in its colour with galls.
7. A solution of sal Martis and alum being mixed in equal quantities, the mixture was turned of a bright blue colour with galls; yet not of so deep a hue, but of a more diluted colour than the solution of sal Martis, without alum. From these experiments we must first of all observe, that the colour, which these waters afford with galls and pomegranate-flowers, is very uncommon. The more iron, that any mineral water contains, it will afford the deeper colour with such astringents: but tho’ I have tried this experiment upon a great many of the ferrugineous waters in Scotland, and also upon the waters of some of the foreign Spaws, I never observed one, that afforded so deep a colour as this, which we now consider. Some of the weakest of them gives only a red or faint purple tincture, and the strongest only a deep purple: but I never saw or heard of any chalybeat water, but this, either in Scotland or elsewhere, that afforded an intense black and inky colour with galls. From which, I think we may venture to conclude, that the water of this Spaw contains a far larger proportion of iron than most, or perhaps than any, other chalybeat water hitherto discovered: and for this reason, I dare say, it will likewise be so much the more preferable to most others in medicinal virtues; which has indeed already appeared by many surprising cures it has performed, and which, I am persuaded, will more fully appear, when its medicinal effects shall be better known.
There must needs be a very great quantity of iron in this water, when it yields as deep a colour with galls as a strong solution of sal Martis. I was indeed at first apprehensive, that this perhaps might not be owing so much to a large and uncommon proportion of chalybeat parts, as to the commixture of alum, which I judged to be in the water. But we see the contrary appears by these trials: for alum of itself affords no tincture with astringents, and, instead of rendering a solution of sal Martis with galls of a more intense colour, rather makes it lighter and more diluted. We see here, that the ferrugineous matter is intirely separated from the water by an infusion of galls. The like also happens by elixation; after which it is almost deprived of its tinging quality. Yet other chalybeat waters lose this quality by much less degree of heat. As there is an ochrous earth separated from all steel waters, when exposed to the air, which subsides to the bottom, and a metalline scum or cremor, which swim on their surface; we shall next consider the appearances, which they make in this water. _Exp._ 8. A solution of saccharum Saturni being dropt into common spring-water, left the upper parts of the water clear and colourless, but formed a lactescency towards the bottom. The same solution being added to the mineral water, soon turned it of a turbid yellow colour, which afterwards subsided, and formed a deep yellow cloud in the bottom of the glass; and below this yellow sediment there adhered to the bottom of the glass a whitish substance, which I took to be the metalline parts of the saccharum Saturni separated from the purer parts of the salt, which were still suspended in the water, and which made it of a muddy whitish colour.
9. Forty drops of oleum tartari per deliquium being added to an ounce of the water, made it of an uniform light yellow colour; but in an hour afterwards there were many small yellow terrene _nubeculæ_ formed in it. These the next day were more conspicuous, being thoroughly separated from the water, and precipitated to the bottom, leaving the water quite clear, as it was before the mixture. A small quantity of this limpid water being taken, it would afford no tincture with galls. It was then all poured off, except so much in the bottom of the glass as contained the above-mentioned clouds: to this there were some galls added, which in half an hour turned these clouds from a light yellow to a deep red colour, but did not change the colour of the water, in which they swam. 10. Immediately after the affusion of ol. tart. p.d. to the water, galls were added to the mixture, which tinged it of a deep and bright red colour. After standing for some time, there were red clouds precipitated to the bottom, and the water continued of a dusky opake red colour.
11. There is a small brook, formerly mentioned, which runs near by these springs; into which the water, that flows from them, is discharged. I observed the stones and channel of this brook all tinged with ochre of a deep yellow colour, so far up as the water of these springs flowed into it; but the channel, which the mineral water ran over before it was mixed with the water of the brook, was very little or nothing discoloured with ochre. As I conjectured what this was owing to, I afterwards took two equal quantities of the mineral water, into one of which I put an equal quantity of common water. In two hours the mixture became less transparent, and appeared yellowish, while the simple mineral water retained its clearness. Next day there was much ochre separated from the mixture, which subsided to the bottom of the glass: but the unmixed mineral water remained still clear and colourless, as at first. All chalybeat waters separate their ochrous parts, when exposed some time to the air; but this separation is made sooner by the commixture of several kinds of salts. Thus we see the ochre in this water is immediately separated and precipitated by the solution of saccharum Saturni.
The oil of tartar causes a precipitation of these ferrugineous parts in the same manner. Which parts must be the sole cause, that the water receives a tincture from galls; since, after they are precipitate, it loses that quality, which they notwithstanding retain even after they are separated from the water. This precipitation of the ochrous parts of the water were the only visible effects that I could perceive to follow from the affusion of the ol. tart. p.d. I remember indeed, when I was at Moffat, I saw the manuscript of Dr. Horsburgh’s experiments upon this mineral water; which appeared to be very accurate; and which I understand are since printed, in a volume lately published by the Philosophical Society at Edinburgh. Amongst these I observed one, which I thought so very remarkable, that I particularly adverted to it. It was the effects of the affusion of ol. tart. p.d. to the water, producing in it clouds, or a coagulation of a green or grass-green colour. I think these were the words; and I own I was something surprised at them.
A solution of vitriolum Martis, mixed with this alkaline oil, does indeed produce a green coagulum: but I could scarcely think, that this, or any other chalybeat water, contained so large a proportion of that vitriol, as to be sufficient to produce these effects, when I considered, that so many writers, which I had seen, upon this subject, have all failed in their attempts of extracting a conspicuous martial vitriol from such mineral waters. I had tried this experiment upon four or five chalybeat springs in Scotland, and likewise upon the Spa and Pyrmont waters, which had been well preserved; but there never resulted any such effects from the mixture of these with oil of tartar, as are related in the above experiment. All the alteration it produced in these waters was the precipitation of an ochrous earth, but without the least appearance of any green colour.
As I looked upon this as a leading experiment in the history of vitriolic waters; as I had often tried it, and as often seen the green coagulum produced with the solution of the factitious vitriol, and never could observe it produced in any of the above water; I began to suspect, that these waters were either not possessed of a vitriolic salt at all, or else, that it was in some respects very different from the factitious vitriol. For these reasons, Dr. Horsburgh’s experiment appeared very extraordinary; tho’ at the same time I was greatly pleased, that I should have the opportunity of repeating it, and of observing those phænomena in this ferrugineous water, which I had sought for in vain in several others. But when I came to make the trial, I was yet more surprised, when I found it misgive, and that the ol. tart. p.d. produced no green colour or coagulum in this mineral water, nor caused any other alteration in it, than the separation of a large quantity of ochrous earth of a yellow colour, exactly the same with what I had observed in the other steel waters.
This failure made me immediately conclude, that I had somehow or other committed an error in the experiment: and tho’ I was pretty sure, that the mineral water, which I had used in it, was quite fresh, yet I could not be so positive as to the oil of tartar, which I suspected to have been long kept. Yet that this could have been the cause of my being so unsuccessful, I could scarcely believe, tho’ indeed I could assign no other. I was sorry, that I had not afterwards an opportunity of repeating this experiment with more accuracy, from which I might have expected to reap more success, as it is perhaps one of the most consequence, that can be performed on this mineral water, as it is capable of demonstrating the existence of a substantial vitriolum Martis in it; which is more than has been hitherto done, or perhaps ever will be done, concerning any one of the vast number of chalybeat waters, which have been yet discovered. When galls are added to the water, at the same time with oil of tartar, instead of its deep blue colour, it affords only a red tincture.
It appears from the 11th experiment, that an addition of common water causes the mineral water to precipitate its ochre; and the reason of this is obvious: for if these ochrous parts be altogether terrene, as they appear to be, and exist in the water unconnected with any other principle, then it must happen, that as these parts are uniformly diffused thro’ the water, in which they are suspended as in a menstruum; by the addition of common water, this menstruum being diluted, the cohesion of these terrene parts must be thereby weakened, and their contact destroyed; so that their menstrual equilibrium being thus taken off, they can be no longer supported in the fluid, but must be precipitated by the force of their own gravity. _Exp._ 12. When the water was exposed for some days to the air, there was a cremor separated from it of a shining chalybeat colour. This, like other kinds of cremor, takes a considerable time to compleat its intire separation from the fluid, out of which it is expelled: for when it was despumated, a new cremor always succeeded, until the whole quantity, which the water contained, was exhausted. 13. When this cremor first appeared on the water, it was of a faint blueish colour; but as it increased, it changed into a deeper and more bright shining blue: and, after longer standing, it became blotched with various colours, as red, orange, yellow, green, blue, purple, and violet.
14. A quantity of the water being put in a gentle heat, this cremor was quickly separated from it, and appeared on the surface of the water. A like quantity of the water, with its cremor already upon its surface, was put over a gentle heat, which by degrees broke the cremor into very small parts; but whether they did evaporate, or precipitate in the water, I could not be certain. But, by other trials, this cremor was found to have a great degree of fixity, bearing a considerable heat without avolation; yet not without the appearance of some of its parts flying off, altho’ most of them were fixed; because what remained lost its fine colours, and was changed into a shining chalybeat colour. 15. The water of the lower spring afforded a much less quantity of the cremor, than the water of the upper spring. It took also a longer time to separate, was of a blueish colour, and had not the vivid colours, which the water of the upper spring shewed. 16. When ol. tart. p.d. and spirit of sal ammoniac were added to the water, it did not separate its cremor.
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