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the Diamond belongs to, and is always classed with, the
twenty-five inflammable substances, and, from its pecu-
liar beauty and arbitrary value, is allowed to be most
important ; and its history furnishes us with some sin-
gular information, as it holds the first rank and place
^STthe cabinet of the mineralogist

Sir Isaac Newton having observed that inflammable
bodies had a greater refraction, in proportion to their
density, than other bodies, and that the diamond resem-
bled them in this property, he was induced to conjecture
that the diamond itself was of an inflammable nature.
The inflammable substances which he employed were
camphor and amber, which he called " fat, sulphurous.



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107

unctuous bodies/* and obseived, that he considered the 1816.
diamond an " unctuous body coagulated.**

This remarkable conjecture of Sir Isaac Newton has
been since partly confirmed by experiment.

The first experiment to prove the combustibility of
the diamond was to expose it in a focus of a great lens,
which was performed in the laboratory of the Grand
Duke of Tuscany, at Florence, in the year 1694,

It was found that, though the diamond was capable
of resisting the effects of the most yiolent heat when the
air was carefully excluded, yet on being exposed to the
action of heat with air it might be entirely consumed !
It became first of a clear red, and soon after appeared to
enlarge in bulk, the result of its entering into combustion :
at length it entirely disappeared, without leaving the
smallest residue.

No attempt was made, however, to determine whether
it was a distinct substance, or one of the inflammable
bodies, until Lavoisier, the celebrated French chemist,
undertook a series of experiments for this purpose. He
exposed the diamond to the heat produced by the focus
of a large lens, in contact with oxygen gas, and was
thus enabled to bum it in a close vessel. After the
combustion was completed, the close vessel or glass jar
(being the receiver) was found filled transparently with
the two gasses, the oxygen and carbonic acid gas. To
prove by experiment that gas produced by the decom-
position of the diamond was composed of a gas called
carbonic acid gas, a portion of it was forced out of the
jar into a tumbler of pellucid lime water, which imme-
diately became turbid.

Now carbonic acid gas has the property or effect to
cause clear or transparent lime water to become turbid ;



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108

I8ia, but oxygen gas has no such property, it will [not in the
least turn lime water turbid.

This experiment proved that the gas arising from the
combustion of the diamond is carbonic acid gas !

And Lavoisier also observed that the air produced by
the combustion precipitated from lime water a white
powder, which he found to be chalk, and that this chalk
was soluble in acids with effervescence, which convinced
him of the resemblance of charcoal to the diamond^
and, consequently, that each of these substances belongs
to a class of inflammable bodies.

The task to ascertain the real nature of it was left to
Mr. Tennant, when he clearly proved that it consists
entirely of charcoal, differing from the usual state of
that substance only by its crystallized form. From the
extreme hardness of the diamond, a stronger degree of
heat was required when exposed merely to the air then
can easily or conveniently be applied in close vessels,
excepty as I have before stated, by means of a burning
lens I But with nitre its combustion may be effected
in a very moderate heat.

He procured a tube of gold which, by having one end
closed, served the purpose of a retort^ a glass bulb being
adapted at the other end to collect the air produced.

He placed a diamond of ten grains with one ounce of
nitre into the tube ; a strong red heat was given to the
tube during an hour and a half ; the fixed air which
came over was not produced by the inflammation of the
diamond, but by the decomposition of the nitre^ for
the fixed air of the diamond was retained by the alkali
of the nitre. When the tube had grown cold, this
alkaline earth, with the whole contents of the tube, was



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109

immediately thrown into a vessel of warm water, and 1816.
dissolved.

This solution then contained nitrous air, fixed air, the
alkali of the nitre, and water.

To obviate the possibility of the fixed air escaping,
as it is well known to have the strongest aflinity for
calcareous earthy a saturated solution of marble in
marine add was poured into the alkaline solution ; the
vessel was then closed, and left undisturbed until the
precipitation had taken place ; the clear liquor was then
poured off from this calcareous precipitate^ and by
trying it with lime water it was found to be free from
fixed air.

The precipitate was then put into a glass globe having
a tube annexed to it, that the quantity of fixed air might
be accurately measured ; quicksilver was then poured
into the glass tube, which already contained the cal-
careous precipitate, as was necessary to fill it; it was next
inverted in a vessel of quicksilver. Some marine acid
was now made to pass up into it.

This marine acid expels or displaces the fixed air from
the calcareous earth, and which fixed air occupies the
top of the tube, and, by its elasticity, presses down the
quicksilver, and in appearance leaves a void in the tube
equal to the space that would occxipj forty ounces of
water.

Now it has always been agreed that the quantity of
fij:ed air produced from ten grains of charcoal occupies
a bulk equal io forty ounces of water.

This experiment clearly proves that the diamond and
the charcoal are constitutionally the same.

I would have ventured to exhibit at this evening's
lecture the decomposition of the diamond, with nitre, in



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110

1816. a gold tube, after Mr. Tennant's method, if the funds
of this institution could and would have permitted it ;
but it will at once be seen, that the expense of a gold
tube, together with a diamond required of ten grains,
places the expense of the experiment beyond the means
of the finances of our Society to entertain for a moment

I have, however, made and appended to the screen a
large drawing or diagram, to elucidate the method
adopted for dissolving or decomposing the diamond, by
collecting the sun's rays with a powerful lens, being, in
my opinion, the most intelligible mode of conveying the
manner practised*

A is an air pump.
T a glass conical form receiver.
G a glass globe form receiver.
F a portable fire-air fiimace.
L a powerful lens.

Open the cock C, between the two glass receivers G
and T, and with the air-pump extract the air from both ;
place the diamond D, of ten grains weight, upon the
platina capsule, supported by the platina legs P, sup-
ported in the inside of the glass globe G.

The apparatus is now ready to receive the oxygen gas.
M in an iron bottle containing pulverized oxide of
manganese, with a tube adapted to be hereafter con-
nected with the tube of the air-pump.

The bottle (iron bottle) M is heated red hot by the
air furnace F at the high temperature required to decom-
pose the manganese ; as part of its oxygen is given ofi^, a
watery vapour is evolved ; when this subsides, lute the
metal tube Y and Z together, and open the cock O,
which will cause the glass jar receiver T, and the globe
receiver G, to be instantly filled with oxygen gas ; then



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112

1816. Among ornaments and luxuries. Diamonds unquestion-
ably occupy, and have ever occupied, the highest rank.
The beauty of this gem depending on its unrivalled
lustre is, no doubt, the circumstance which originally
brought it into notice, and certainly, notwithstanding the
smallness of its bulk, there is no substance, natural or
artificial, that can sustain any comparison with it in this
respect The varied and vivid refractions of the Opal
— the refreshing tint of the Emerald — the high coloured
lustre that distinguishes the Ruhy — the ethereal light
that streams from the Sapphire — and the golden rays
that emanate from the Topaz — ^beautiful as they are,
seem lost, at a small distafice, in comparison with the
Diamond, which, although it has no colour of its own,
imbibes the pure solar ray, reflects it with undiminished
intensity, and refracts it into such prismatic colours,
cors\nmng urieqiLolled briUiancy ; and whether blazing
on the crown of state, or diffusing its starry radiance
from the breast of titled merit, in courts or high solem-
nities, it proclaims to the most distant circle of the
surrounding crowd the person of the monarch, of the
noblesse, or of the beauty.

Diamonds of a large size are so rare, that their num-
ber scarcely amounts to twenty-five in the world, and,
perhaps, only about two-thirds of that number in Europe.
These are nearly in the possession of sovereign Princes ;
hence the acquisition of a moderate size diamond is
what mere money cannot always command.

When the Czar Peter the Great, and his whole army,
was surrounded by the Turks, he owed his safety to the
fascinating splendgur of the diamonds of his Empress I

The regent diamond of France was played by the
Abbe Sieyes with such success before the Sovereign of



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113

Prussia as to produce for the service of France 40,000 1816.
horses, with their equipments.

The only places where this extraordinary gem has
been found, in modem times, are the southern parts of
India Proper, the peninsula of Malacca, the island of
Borneo, and the mountainous district called Serro do Frio,
in the Brazils. Neither the rock in which it occurs, nor
the other minerals with which it is accompanied, in
Malacca, and in the island of Borneo, are at all known ;
but in the southern part of India the class of minerals
which accompany diamonds is better understood.

There are four diamond mines in the East, three of
which are situate within a few days* journey of Golconda.
One of these is called Ralconda, which produces in
general very small stones, seldom more than three carats
in weight. The mine called Coulour is famous for
diamonds of a large size — ^from ten to forty carats ; now
a carat of diamond is equal to four grains, which must
not be confounded with a carat of gold, as a carat of
gold is twelve grains.

It was in the mine of Coulour that the wonderM
diamond of Aurez Seb, the Great Mogul, was found, and
which weighed 795 carats. The stones in this mine are
not very clear, and, extraordinary to tell, are generally
tinged with the colour of the soil. There are generally
many thousands of men, women, and children, at work
in this mine.

The third mine is that of Samalpour, which lays
nearer to Bengal This mine is actually in the bed of the
river, and is the mine which produces the natural sparks,
or diamond points, used by glaziers for the purpose of
dividing plates of glass.

The mine in the island of Borneo is in the bed of the



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114

1816. river ; but we are but little acquainted with this mine,
for the Queen who reigns in that part of the island will
not allow any stranger to visit the place, nor, indeed, to
have any dealings in diamonds. The stones are generally
smuggled to Batavia, and bought up by the Dutch, who
say that they seldom knew that any one stone was sold
from this mine that weighed more than from twenty to
thirty carats.

The other diamond mines are situate in the Brazils,
about three hundred and fifty miles north of Rio de
Janeiro, in the diamond district, and which are called the
diamond mines of Serro do Frio, the town of Tejuco being
the capital, and the principal mine is upon a river called
Jagitonhona ; and no foreigner had ever been permitted
to visit these mines until August, 1809, when Mr. John
Mawe, of the Strand, the author of the " Mineralogy of
Derbyshire,'* obtained permission, from the Prince Regent
of Portugal, through the influence of our Ambassador at
the Brazils, to explore the diamond mines of Serro do
Frio. The minister Cond6 de Linhares ordered pass-
ports and letters of recommendation immediately to be
made out, sanctioned by our Brazilian Ambassador, Lord
Strangford ; and, on the 9th of August, Mr. Mawe set
off on his journey, attended strictly by a file of soldiers,
and, no doubt, watched and treated by all the captains
of the stations with the most suspicious and jealous
feeling. On the 17th of September, Mr. Mawe arrived,
with the two soldiers, at Tejuco, the capital of the dia-
mond mines, and delivered his letters to Mr. Fernando
de Camara, the Governor. The stratum of materials in
which the diamonds are discovered is called by the
natives cascalhdo. It is composed of granite, fieldspar,
hornblende, quartz, mica ; no metallic substances, except



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115

some grains of gold and oxide of iron, appear. This 1816.
composition^ or cascalhdo, is raked into troughs, with
water passing through. The largest stones are thrown out,
and the residue examined with great care for diamonds,
and when a negro finds one he stands up and claps his
hands, and holds the gem between his fore-finger and
thumb ; the overseer receives it from him, and deposits
it in a bowl suspended from a rafter of the awning, and
which bowl is half filled with water. It is said that, in-
cluding all the mines in the Brazils, near 10,000 people,
including men, women, and children, are employed ;
and when a negro finds a diamond equal in weight to
seventeen and a half carats, he obtains his libertv.
During Mr. Mawe's visit, it so occurred that one of six-
teen and a half carats was found ; but since that period
very few have been found that exceed that weight ; and
it is said that not one of twenty-five to thirty carats has
been discovered for many years. Providence, in his
wisdom, it appears, has so ordered, that the diamond,
the most beautiful of all the gems, is the most rare ; that
gold, the most durable of all the metals, is the most
scarce ; and that iron, the most useful of all the metals,
is abuiidant everywhere I



Colour of Diamonds.

The diamond is either colourless, or light brown, pass-
ing into wine colour ; cinnamon brown, passing into
blackish j pale green, passing into yellowish green ;
blueish grey, passing into Prussian blue ; and a pink
colour ; but when of these colours they are generally of
a dull faint tinge, which much reduces their value.



1 2



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116

1816. The most valuable are those which are of a dear drop
of water, and hence called diamonds (by some'persons
or traders) of the first water, others diamonds of the
second water, and so on, according to their purity.



External Forms op the Diamond,

Ist, The Octahedron*

2d, The Octahedron with bevelled edges.

Sd, The Dodecahedron accurately bevelled in all its
angles.

4th, The Octahedron, in which each plane is divided
into six ; so that the figure has 48 triangular faces.

5th, The Octahedron, with the edges trmicated.

6th, The Dodecahedron.

7th, The Sided Prism accumulated by three planes.

8th, The Rhomboidal Dodecahedron.

9th, The same figure, with the angles less acute.
10th, The Octahedron, having each of its angles
truncated, and also the extremities truncated.
11th, The Twin Crystal
The Integrant Molecule being the Tetahedron.
It appears, however, that diamonds are generally of
the Amorphous ^rms.

We can readily suppose that all amorphous stones of
gems, &c., except the diamond, have been rounded by
attritmij perhaps at the period of the flood ; but as
diamonds are the hardest of all substances, and are never
found in sufficient quantities to have this effect, we are
unable to account for this alteration of Nature ; for the
lapidary is only enabled to cut the diamond by pulverized
diamond dust, as it is called, which dust is obtained from



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117

pulverizing the bad-coloured diamonds in a small steel 1816*
mortar, the particles of which will (by using a high
magnifier) be found Tetrahedrons. On account of this
excessive hardness, mineralogists agree that the amor-
phous form cannot be from the effect o( attrition.

The diamond is far from being difficult of fracture ; a
slight blow with the liammer will readily break it, and
then exhibits its straight lamellar structure. It has, in
fact, a distinct foliated texture, similar to mica: the
cleavage is fowrfbldy parallel to the face of the octahe-
dron, the fragments being either octahedral or tetrahe-
dral. Its hardness is twenty ; lustre, four. It has also
the quality, on being rubbed, of becoming electric, even
before it is cut, which is not the case with any other
crystallized gem.

As the diamond will bring nearly the same value in
all European countries, it is of more importance than
persons generally are aware of to be conversant with the
mode of calculating its price, conformably to its size, by
some general rule, because it is the most secure way for
a person to carry his property from one country to
another ; it thereby becomes desirable to be a judge in
the value of the diamond, to enable him to convert his
property into diamonds, whose prices seldom fluctuate
more than 5 to 7^ per cent. ; whereas biUs of exchange
are, at all times, dubious and expensive, and specie
cannot, in many countries, be had ; and, if purchased
with biUs, the exchange makes it expensive.

When I speak of diamonds being thus purchased, I
mean diamonds unset — in the state they are to be found
in the hands of the diamond merchant at the capital of
every country in Europe, and they will be found so
portable that £100,000 may be compressed into a mode-



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118

1816. rate size pocket-book. I have made a slight diagram
of six sizes, viz. : —

Weight of 1 carat, or 4 grains

2 carats, or 8 grains

3 carats, or 12 grains

4 carats, or 16 grains

5 carats, or 20 grains

6 carats, or 24 grains

The sizes generally upon sale are from, perhaps, a
quarter of a carat to six carats, and between one carat
and five are the sizes generally worn by gentlemen on
the shirt or cravat.

The calculation of the value of diamonds of the above-
named six sizes, and, indeed, of all diamonds, however
large, are governed in conversion by the following
fixed rule: —

Suppose a diamond of two carats in the natural state
or rough state. As it loses in cutting about one half,
double the weight ; then square the weight so doubled,
which produces the product ; then multiply the product
by two, which produces the sum or supposed value of the
gem.

Thus a diamond of 2 carats,

2 or double to cover the loss in

— cutting.
4

4 Square the amount.

16
2 Multiply the sum by 2

£32 The value of a stone of 2

— carats.



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119

Suppose one of 50 carats* II8T6.

2

100
100



10,000
2

£20,000



In fact, a diamond of double its weight is always four
times in value.

I have already mentioned that there are scarcely
twenty large diamonds in Europe and Asia, and these
almost invariably in the possession of foreign princes ;
and are set in the hilt of the dress sword, or in the
sceptre which the Sovereign holds on state occasions,
and with foreign princes frequently upon the arm. And
as these are only exhibited to the public, and at a dis-
tance, on levee days, the greatest difficulty has arisen to
those few travellers who may have had the opportunity
to calculate upon their magnitude or size, from recollec-
tioriy or from an appearance of them^

It appeared to me that the only mode to be adopted
to arrive at conclusions that would, in some degee, iden-
tify their sizes, would be to make a vitrification whose
specific gravity should be the same as the specific gravity
of the diamond, which is 3,500, water being 1,000 in an
equal bulk ; diamond being, as near as possible, three
and a half times as heavy as water.

I was well aware of the many and repeated trials, in
experimentalizing, to make a paste, or body of glass,



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120

1816. exactly of this gravity, viz., three and a half times the
weight of water.

I could not find any natural mineral, except the mala-
chite, of such exact specific gravity, and this mineral
being opaque, it would fail in conveying to the eye the
true appearance of the size.

The specific gravity of crystal is only 2,650, and the
specific gravity of white flint glass 3,100, falling short of
what I required.

I conceived it possible to impregnate white paste glass
with a metallic oxide, and de-oxidising or vitrifying the
whole mass or body ; in which I succeeded, with anti-
mony for its base. Thereby I procured a brilliant trans-
parent yellow paste, the cubic inch of which proved to
be three and a half times the weight of water.

Of this yellow brilliant paste I have had a cubic inch
mathematically cut This cubic inch is upon the table
before you ; and to prove to you that I have been suc-
cessful in the experiment, I will try it by the hydrostatic
balance. If the weight, then, of any substance in air be
divided by what it loses in water, the qicotient will shew
how much that body is heavier than its btUk of water.

You perceive that this cubic inch weighs in air 35
dwts. 17^ grains, and that it loses in water, that is, when
weighed in water, 10 dwts. 5 grains ; consequently, if we
multiply 10 dwts. 5 grains by 3^, its product is 35 dwts.
17^ grains.

Although so far successful, I must content myself in
producing all the diamonds of a yellow colour instead of
a white colour, because I could not obtain any other
vitrified transparent composition of the true specific
gravity ; and this, you will perceive, is fortunately of a
most exquisite brilliancy*



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121

l8t What was next wanting was to obtain the infer- 1816.
mation of the exact weight of each of the different large
diamonds, perhaps about twenty in number, said to be
in the known world.

2dly. What was the form of each.

And 3dly. Whether brilliant-cut, rose-cut, or flat
table form.

The different EncyclopsBdias, and the History of the
Courts of the several countries possessing these diamonds,
gave me the clue to most, except the diamonds belonging
to the King of Persia, the weight and form of which were
lately brought over to England by Sir John Malcolm.

I applied to some of the Directors of the East India
Company to be permitted to copy the drawings of the six
large diamonds belonging to the King of Persia, who
gave me every facility, and thereby enabled me this
evening to exhibit their sizes and forms, in common with
others, making the models tolerably complete, in size
and shape ; altogether, or in the whole, of twenty-four
stones ; and the brilliancy of them, owing to the acci-
dental success in the vitrification of the oxide, is alone
very favourable for our illustration in this evening's lec-
ture. I will endeavour to enter into the history of each,
without vouching for the authenticity of the statements,
because there have been so many various versions in the
reports ; yet, after much research, I hope that I have
taken the most probable data for our guidance and com-
prehension.

In England, during the last century, we can only cal-
culate of having had four very large diamonds, at least
of more than 36 carats in weight, or the value of
£10,000.



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122



1816. 1st. The Auckland.

The Auckland diamond is understood to be in the
possession of Lord Auckland's family, and was brought
from Hindostan by a branch of the Auckland family. It
weighs 36 carats, and its value, according to the table,
is £10,368 ; but, in consequence of a little deformity in
its^rm, £8,000, report says, is the largest offer made
for it



2nd. British Crown.

The largest diamond in the British Crown weighs
only 36 carats. It is of a long quadrilateral form, of
inferior water, and extremely thin ; hence its great spread
for its weight ; its value, according to the table of calcu-
lation, is £10,368.

3rd. The Piggot.

The Piggot diamond was brought to England by
Earl Piggot, the Governor General of India. It
remained with the Shropshire family of this name for
many years, who were unable to dispose of it by private