Volume I Part 25 (1/2)

The higher and lower parts of mora.s.ses were necessarily produced at different periods of time, see Note XVII. and would thus originally be formed in strata of different ages. For when an old wood perished, and produced a mora.s.s, many centuries would elapse before another wood could grow and perish again upon the same ground, which would thus produce a new stratum of mora.s.s over the other, differing indeed princ.i.p.ally in its age, and perhaps, as the timber might be different, in the proportions of its component parts.

Now if we suppose the lowermost stratum of a mora.s.s become ignited, like fermenting hay, (after whatever could be carried away by solution in water was gone,) what would happen? Certainly the inflammable part, the oil, sulphur, or bitumen, would burn away, and be evaporated in air; and the fixed parts would be left, as clay, lime, and iron; while some of the calcareous earth would join with the siliceous acid, and produce sand, or with the argillaceous earth, and produce marl. Thence after many centuries another bed would take fire, but with less degree of ignition, and with a greater body of mora.s.s over it, what then would happen? The bitumen and sulphur would rise and might become condensed under an impervious stratum, which might not be ignited, and there form coal of different purities according to its degree of fluidity, which would permit some of the clay to subside through it into the place from which it was sublimed.

Some centuries afterwards another similar process might take place, and either thicken the coal-bed, or produce a new clay-bed, or marl, or sand, or deposit iron upon it, according to the concomitant circ.u.mstances above mentioned.

I do not mean to contend that a few ma.s.ses of some materials may not have been rolled together by currents, when the mountains were much more elevated than at present, and in consequence the rivers broader and more rapid, and the storms of rain and wind greater both in quant.i.ty and force. Some gravel-beds may have been thus washed from the mountains; and some white clay washed from mora.s.ses into valleys beneath them; and some ochres of iron dissolved and again deposited by water; and some calcareous depositions from water, (as the bank for instance on which stand the houses at Matlock-bath;) but these are of small extent or consequence compared to the primitive rocks of granite or porpyhry which form the nucleus of the earth, or to the immense strata of limestone which crust over the greatest part of this granite or porphyry; or lastly to the very extensive beds of clay, marl, sandstone, coal, and iron, which were probably for many millions of years the only parts of our continents and islands, which were then elevated above the level of the sea, and which on that account became covered with vegetation, and thence acquired their later or superinc.u.mbent strata, which const.i.tute, what some have termed, the new world.

There is another source of clay, and that of the finest kind, from decomposed granite, this is of a snowy white and mixed with mining particles of mica, of this kind is an earth from the country of Cherokees. Other kinds are from less pure lavas; Mr. Ferber a.s.serts that the sulphurous steams from Mount Vesuvius convert the lava into clay.

”The lavas of the antient Solfatara volcano have been undoubtedly of a vitreous nature, and these appear at present argillaceous. Some fragments of this lava are but half or at one side changed into clay, which either is viscid or ductile, or hard and stoney. Clays by fire are deprived of their coherent quality, which cannot be restored to them by pulverization, nor by humectation. But the sulphureous Solfatara steams restore it, as may be easily observed on the broken pots wherein they gather the sal ammoniac; though very well baked and burnt at Naples they are mollified again by the acid steams into a viscid clay which keeps the former fire-burnt colour.” Travels in Italy, p. 156.

NOTE XXI.--ENAMELS.

_Smear'd her huge dragons with metallic hues, With golden purples, and cobaltic blues;_

CANTO II. l. 287.

The fine bright purples or rose colours which we see on china cups are not producible with any other material except gold, manganese indeed gives a purple but of a very different kind.

In Europe the application of gold to these purposes appears to be of modern invention. Ca.s.sius's discovery of the precipitate of gold by tin, and the use of that precipitate for colouring gla.s.s and enamels, are now generally known, but though the precipitate with tin be more successful in producing the ruby gla.s.s, or the colourless gla.s.s which becomes red by subsequent ignition, the tin probably contributing to prevent the gold from separating, (which it is very liable to do during the fusion; yet, for enamels, the precipitates made by alcaline salts answer equally well, and give a finer red, the colour produced by the tin precipitate being a bluish purple, but with the others a rose red. I am informed that some of our best artists prefer aurum fulminans, mixing it, before it has become dry, with the white composition or enamel flux; when once it is divided by the other matter, it is ground with great safety, and without the least danger of explosion, whether moist or dry. The colour is remarkably improved and brought forth by long grinding, which accordingly makes an essential circ.u.mstance in the process.

The precipitates of gold, and the colcothar or other red preparations of iron, are called _tender_ colours. The heat must be no greater than is just sufficient to make the enamel run upon the piece, for if greater, the colours will be destroyed or changed to a different kind. When the vitreous matter has just become fluid it seems as if the coloured metallic calx remained barely _intermixed_ with it, like a coloured powder of exquisite tenuity suspended in water: but by stronger fire the calx is _dissolved_, and metallic colours are altered by _solution_ in gla.s.s as well as in acids or alcalies.

The Saxon mines have till very lately almost exclusively supplied the rest of Europe with cobalt, or rather with its preparations, zaffre and smalt, for the exportation of the ore itself is there a capital crime.

Hungary, Spain, Sweden, and some other parts of the continent, are now said to afford cobalts equal to the Saxon, and specimens have been discovered in our own island, both in Cornwall and in Scotland; but hitherto in no great quant.i.ty.

Calces of cobalt and of copper differ very materially from those above mentioned in their application for colouring enamels. In those the calx has previously acquired the intended colour, a colour which bears a red heat without injury, and all that remains is to fix it on the piece by a vitreous flux. But the blue colour of cobalt, and the green or bluish green of copper, are _produced_ by vitrification, that is, by _solution_ in the gla.s.s, and a strong fire is necessary for their perfection. These calces therefore, when mixed with the enamel flux, are melted in crucibles, once or oftener, and the deep coloured opake gla.s.s, thence resulting, is ground into unpalpable powder, and used for enamel. One part of either of these calces is put to ten, sixteen, or twenty parts of the flux, according to the depth of colour required. The heat of the enamel kiln is only a full red, such as is marked on Mr. Wedgwood's thermometer 6 degrees. It is therefore necessary that the flux be so adjusted as to melt in that low heat. The usual materials are flint, or flint-gla.s.s, with a due proportion of red-led, or borax, or both, and sometimes a little tin calx to give opacity.

_Ka-o-lin_ is the name given by the Chinese to their porcelain clay, and _pe-tun-tse_ to the other ingredient in their China ware. Specimens of both these have been brought into England, and found to agree in quality with some of our own materials. Kaolin is the very same with the clay called in Cornwall [Transcriber's note: word missing] and the petuntse is a granite similar to the Cornish moorstone. There are differences, both in the Chinese petuntses, and the English moorstones; all of them contain micaceous and quartzy particles, in greater or less quant.i.ty, along with feltspat, which last is the essential ingredient for the porcelain manufactory. The only injurious material commonly found in them is iron, which discolours the ware in proportion to its quant.i.ty, and which our moorstones are perhaps more frequently tainted with than the Chinese. Very fine porcelain has been made from English materials but the nature of the manufacture renders the process precarious and the profit hazardous; for the semivitrification, which const.i.tutes porcelain, is necessarily accompanied with a degree of softness, or semifusion, so that the vessels are liable to have their forms altered in the kiln, or to run together with any accidental augmentations of the fire.

NOTE XXII.--PORTLAND VASE.

_Or bid Mortality rejoice or mourn O'er the fine forms of Portland's mystic urn._

CANTO II. l. 319.

The celebrated funereal vase, long in possession of the Barberini family, and lately purchased by the Duke of Portland for a thousand guineas, is about ten inches high and six in diameter in the broadest part. The figures are of most exquisite workmans.h.i.+p in bas relief of white opake gla.s.s, raised on a ground of deep blue gla.s.s, which appears black except when held against the light. Mr. Wedgwood is of opinion from many circ.u.mstances that the figures have been made by cutting away the external crust of white opake gla.s.s, in the manner the finest cameo's have been produced, and that it must thence have been the labour of a great many years. Some antiquarians have placed the time of its production many centuries before the christian aera; as sculpture was said to have been declining in respect to its excellence in the time of Alexander the Great. See an account of the Barberini or Portland vase by M. D'Hancarville, and by Mr. Wedgwood.

Many opinions and conjectures have been published concerning the figures on this celebrated vase. Having carefully examined one of Mr. Wedgwood's beautiful copies of this wonderful production of art, I shall add one more conjecture to the number.

Mr. Wedgwood has well observed that it does not seem probable that the Portland vase was purposely made for the ashes of any particular person deceased, because many years must have been necessary for its production. Hence it may be concluded, that the subject of its embellishments is not private history but of a general nature. This subject appears to me to be well chosen, and the story to be finely told; and that it represents what in antient times engaged the attention of philosophers, poets, and heroes, I mean a part of the Eleusinian mysteries.

These mysteries were invented in Aegypt, and afterwards transferred to Greece, and flourished more particularly at Athens, which was at the same time the seat of the fine arts. They consisted of scenical exhibitions representing and inculcating the expectation of a future life after death, and on this account were encouraged by the government, insomuch that the Athenian laws punished a discovery of their secrets with death. Dr. Warburton has with great learning and ingenuity shewn that the descent of Aeneas into h.e.l.l, described in the Sixth Book of Virgil, is a poetical account of the representations of the future state in the Eleusinian mysteries. Divine Legation, Vol. I. p. 210.

And though some writers have differed in opinion from Dr. Warburton on this subject, because Virgil has introduced some of his own heroes into the Elysian fields, as Deiphobus, Palinurus, and Dido, in the same manner as Homer had done before him, yet it is agreed that the received notions about a future state were exhibited in these mysteries, and as these poets described those received notions, they may be said, as far as these religious doctrines were concerned, to have described the mysteries.

Now as these were emblematic exhibitions they must have been as well adapted to the purposes of sculpture as of poetry, which indeed does not seem to have been uncommon, since one compartment of figures in the sheild of Aeneas represented the regions of Tartarus. Aen. Lib. X. The procession of torches, which according to M. De St. Croix was exhibited in these mysteries, is still to be seen in ba.s.so relievo, discovered by Spon and Wheler. Memoires sur le Mysteres par De St. Croix. 1784. And it is very probable that the beautiful gem representing the marriage of Cupid and Psyche, as described by Apuleus, was originally descriptive of another part of the exhibitions in these mysteries, though afterwards it became a common subject of antient art. See Divine Legat. Vol. I. p.

323. What subject could have been imagined so sublime for the ornaments of a funereal urn as the mortality of all things and their resuscitation? Where could the designer be supplied with emblems for this purpose, before the Christian era, but from the Eleusinian mysteries?

1. The exhibitions of the mysteries were of two kinds, those which the people were permitted to see, and those which were only shewn to the initiated. Concerning the latter, Aristides calls them ”the most shocking and most ravis.h.i.+ng representations.” And Stoboeus a.s.serts that the initiation into the grand mysteries exactly resembles death. Divine Legat. Vol. I. p. 280, and p. 272. And Virgil in his entrance to the shades below, amongst other things of terrible form, mentions death.