The Botanic Garden

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7. ANGLES OF SILICEOUS SAND.

In many rocks of siliceous sand the particles retain their angular form,
and in some beds of loose sand, of which there is one of considerable
purity a few yards beneath the marl at Normington about a mile south of
Derby. Other siliceous sands have had their angles rounded off, like the
pebbles in gravel-beds. These seem to owe their globular form to two
causes; one to their attrition against each other, when they may for
centuries have lain at the bottom of the sea, or of rivers; where they
may have been progressively accumulated, and thus progressively at the
same time rubbed upon each other by the dashing of the water, and where
they would be more easily rolled over each other by their gravity being
so much less than in air. This is evidently now going on in the river
Derwent, for though there are no limestone rocks for ten or fifteen
miles above Derby, yet a great part of the river-gravel at Derby
consists of limestone nodules, whose angles are quite worn off in their
descent down the stream.

There is however another cause which must have contributed to round the
angles both of calcareous and siliceous fragments; and that is, their
solubility in water; calcareous earth is perpetually found suspended in
the waters which pass over it; and the earth of flints was observed by
Bergman to be contained in water in the proportion of one grain to a
gallon. Kirwan's Mineralogy, p. 107. In boiling water, however, it is
soluble in much greater proportion, as appears from the siliceous earth
sublimed in the distillation of fluor acid in glass vessels; and from
the basons of calcedony which surrounded the jets of hot water near
mount Heccla in Iceland. Troil on Iceland. It is probable most siliceous
sands or pebbles have at some ages of the world been long exposed to
aqueous steams raised by subterranean fires. And if fragments of stone
were long immersed in a fluid menstrum, their angular parts would be
first dissolved, on account of their greater surface.

Many beds of siliceous gravel are cemented together by a siliceous
cement, and are called breccia; as the plumb-pudding stones of
Hartfordshire, and the walls of a subterraneous temple excavated by Mr.
Curzon, at Hagley near Rugely in Staffordfshire; these may have been
exposed to great heat as they were immersed in water; which water under
great pressure of superincumbent materials may have been rendered red-
hot, as in Papin's digester; and have thus possessed powers of solution
with which we are unacquainted.

8. BASALTES AND GRANITES.

Another source of siliceous stones is from the granite, or basaltes, or
porphyries, which are of different hardnesses according to the materials
of their composition, or to the fire they have undergone; such are the
stones of Arthur's-hill near Edinburgh, of the Giant's Causway in
Ireland, and of Charnwood Forest in Leicestershire; the uppermost
stratum of which last seems to have been cracked either by its
elevation, or by its hastily cooling after ignition by the contact of
dews or snows, and thus breaks into angular fragments, such as the
streets of London are paved with; or have had their angles rounded by
attrition or by partial solution; and have thus formed the common paving
stones or bowlers; as well as the gravel, which is often rolled into
strata amid the siliceous sand-beds, which are either formed or
collected in the sea.

In what manner such a mass of crystallized matter as the Giant's Causway
and similar columns of basaltes, could have been raised without other
volcanic appearances, may be a matter not easy to comprehend; but there
is another power in nature besides that of expansile vapour which may
have raised some materials which have previously been in igneous or
aqueous solution; and that is the act of congelation. When the water in
the experiments above related of Major Williams had by congelation
thrown out the plugs from the bomb-shells, a column of ice rose from the
hole of the bomb six or eight inches high. Other bodies I suspect
increase in bulk which crystallize in cooling, as iron and type-metal. I
remember pouring eight or ten pounds of melted brimstone into a pot to
cool and was surprized to see after a little time a part of the fluid
beneath break a hole in the congealed crust above it, and gradually rise
into a promontory several inches high; the basaltes has many marks of
fusion and of crystallization and may thence, as well as many other
kinds of rocks, as of spar, marble, petrosilex, jasper, &c. have been
raised by the power of congelation, a power whose quantity has not yet
been ascertained, and perhaps greater and more universal than that of
vapours expanded by heat. These basaltic columns rise sometimes out of
mountains of granite itself, as mentioned by Dr. Beddoes, (Phil.
Transact. Vol. LXXX.) and as they seem to consist of similar materials
more completely fused, there is still greater reason to believe them to
have been elevated in the cooling or crystallization of the mass. See
note XXIV.

NOTE XX.--CLAY.

_Whence ductile Clays in wide expansion spread,
Soft as the Cygnet's down, their snow-white bed._

CANTO II. l. 277.

The philosophers, who have attended to the formation of the earth, have
acknowledged two great agents in producing the various changes which the
terraqueous globe has undergone, and these are water and fire. Some of
them have perhaps ascribed too much to one of these great agents of
nature, and some to the other. They have generally agreed that the
stratification of materials could only be produced from sediments or
precipitations, which were previously mixed or dissolved in the sea; and
that whatever effects were produced by fire were performed afterwards.

There is however great difficulty in accounting for the universal
stratification of the solid globe of the earth in this manner, since
many of the materials, which appear in strata, could not have been
suspended in water; as the nodules of flint in chalk-beds, the extensive
beds of shells, and lastly the strata of coal, clay, sand, and iron-ore,
which in most coal-countries lie from five to seven times alternately
stratified over each other, and none of them are soluble in water. Add
to this if a solution of them or a mixture of them in water could be
supposed, the cause of that solution must cease before a precipitation
could commence.

1. The great masses of lava, under the various names of granite,
porphyry, toadstone, moor-stone, rag, and slate, which constitute the
old world, may have acquired the stratification, which some of them
appear to possess, by their having been formed by successive eruptions
of a fluid mass, which at different periods of antient time arose from
volcanic shafts and covered each other, the surface of the interior mass
of lava would cool and become solid before the superincumbent stratum
was poured over it; to the same cause may be ascribed their different
compositions and textures, which are scarcely the same in any two parts
of the world.

2. The stratifications of the great masses of limestone, which were
produced from sea-shells, seem to have been formed by the different
times at which the innumerable shells were produced and deposited. A
colony of echini, or madrepores, or cornua ammonis, lived and perished
in one period of time; in another a new colony of either similar or
different shells lived and died over the former ones, producing a
stratum of more recent shell over a stratum of others which had began to
petrify or to become marble; and thus from unknown depths to what are
now the summits of mountains the limestone is disposed in strata of
varying solidity and colour. These have afterwards undergone variety of
changes by their solution and deposition from the water in which they
were immersed, or from having been exposed to great heat under great
pressure, according to the ingenious theory of Dr. Hutton. Edinb.
Transact. Vol. I. See Note XVI.

3. In most of the coal-countries of this island there are from five to
seven beds of coal stratified with an equal number of beds, though of
much greater thickness, of clay and sandstone, and occasionally of iron-
ores. In what manner to account for the stratification of these
materials seems to be a problem of greater difficulty. Philosophers have
generally supposed that they have been arranged by the currents of the
sea; but considering their insolubility in water, and their almost
similar specific gravity, an accumulation of them in such distinct beds
from this cause is altogether inconceiveable, though some coal-countries
bear marks of having been at some time immersed beneath the waves and
raised again by subterranean fires.

The higher and lower parts of morasses 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 morass, many centuries would elapse before another wood could
grow and perish again upon the same ground, which would thus produce a
new stratum of morass over the other, differing indeed principally 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 morass 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 morass 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
circumstances above mentioned.

I do not mean to contend that a few masses 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 quantity and
force. Some gravel-beds may have been thus washed from the mountains;
and some white clay washed from morasses 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 superincumbent strata, which constitute,
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 asserts 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. Cassius's discovery of the precipitate of gold by tin,
and the use of that precipitate for colouring glass and enamels, are now
generally known, but though the precipitate with tin be more successful
in producing the ruby glass, or the colourless glass 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 circumstance 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
glass 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 quantity.

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 glass, 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 glass, 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-glass, 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 quantity,
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 quantity,
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 constitutes
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 workmanship in bas relief of
white opake glass, raised on a ground of deep blue glass, which appears
black except when held against the light. Mr. Wedgwood is of opinion
from many circumstances that the figures have been made by cutting away
the external crust of white opake glass, 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 hell, 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 basso 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 ravishing representations." And Stoboeus asserts 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.
Aen. VI. This part of the exhibition seems to be represented in one of
the compartments of the Portland vase.

Three figures of exquisite workmanship are placed by the side of a
ruined column whose capital is fallen off, and lies at their feet with
other disjointed stones, they sit on loose piles of stone beneath a
tree, which has not the leaves of any evergreen of this climate, but may
be supposed to be an elm, which Virgil places near the entrance of the
infernal regions, and adds, that a dream was believed to dwell under
every leaf of it. Aen. VI. l. 281. In the midst of this group reclines a
female figure in a dying attitude, in which extreme languor is
beautifully represented, in her hand is an inverted torch, an antient
emblem of extinguished life, the elbow of the same arm resting on a
stone supports her as she sinks, while the other hand is raised and
thrown over her drooping head, in some measure sustaining it and gives
with great art the idea of fainting lassitude. On the right of her sits
a man, and on the left a woman, both supporting themselves on their
arms, as people are liable to do when they are thinking intensely. They
have their backs towards the dying figure, yet with their faces turned
towards her, as if seriously contemplating her situation, but without
stretching out their hands to assist her.

This central figure then appears to me to be an hieroglyphic or
Eleusinian emblem of MORTAL LIFE, that is, the lethum, or death,
mentioned by Virgil amongst the terrible things exhibited at the
beginning of the mysteries. The inverted torch shews the figure to be
emblematic, if it had been designed to represent a real person in the
act of dying there had been no necessity for the expiring torch, as the
dying figure alone would have been sufficiently intelligible;--it would
have been as absurd as to have put an inverted torch into the hand of a
real person at the time of his expiring. Besides if this figure had
represented a real dying person would not the other figures, or one of
them at least, have stretched out a hand to support her, to have eased
her fall among loose stones, or to have smoothed her pillow? These
circumstances evince that the figure is an emblem, and therefore could
not be a representation of the private history of any particular family
or event.

The man and woman on each side of the dying figure must be considered as
emblems, both from their similarity of situation and dress to the middle
figure, and their being grouped along with it. These I think are
hieroglyphic or Eleusinian emblems of HUMANKIND, with their backs toward
the dying figure of MORTAL LIFE, unwilling to associate with her, yet
turning back their serious and attentive countenances, curious indeed to
behold, yet sorry to contemplate their latter end. These figures bring
strongly to one's mind the Adam and Eve of sacred writ, whom some have
supposed to have been allegorical or hieroglyphic persons of Aegyptian
origin, but of more antient date, amongst whom I think is Dr. Warburton.
According to this opinion Adam and Eve were the names of two
hieroglyphic figures representing the early state of mankind; Abel was
the name of an hieroglyphic figure representing the age of pasturage,
and Cain the name of another hieroglyphic symbol representing the age of
agriculture, at which time the uses of iron were discovered. And as the
people who cultivated the earth and built houses would increase in
numbers much faster by their greater production of food, they would
readily conquer or destroy the people who were sustained by pasturage,
which was typified by Cain slaying Abel.

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