Page images
PDF
EPUB

E 1797

D I C TI O N A RY
D

Ο Ν A

OR, A

OF

ARTS, SCIENCES,

AND

MISCELLANEOUS LITERATURE;

Constructed on a PLAN,

BY WHICH,

THE DIFFERENT SCIENCES AND ARTS

Are digefted into the FORM of Distinct
TRE A TI SES OR SYSTEMS,

COMPR III ENDINO

The HISTORY, THEOR Y, and PRACTICE, of each,
according to the Latest Discoveries and Improvements;

AND FULL EXPLANATIONS GIVEN OF THE
VARIOUS DETACHED PARTS OF KNOWLEDGE,

WHETHER RELATING TO

NATURAL and ARTIFICIAL Objects, or to Matters EccLEsiASTICAL,

Civil, MILITARY, COMMERCIAL, &c.
Including ELUCIDATIONS of the most important Topics relative to RELIGION, MORALS,

MANNERS, and the OECONOMY of LIFE:

TOGETHER WIT II

A DESCRIPTION of all the Countries, Cities, principal Mountains, Seas, Rivers, 6c.

throughout the WORLD);
A General HISTORY, Ancient and Modern, of the different Empires, Kingdoms, and States;

AND

An Account of the Lives of the most Eminent Persons in every Nation,

from the earliest ages down to the present times.

i

Compiled from the writings of the best Autbors, in sever.il languages; the mojl approved Dictionaries, as well of general frience as of its partia
cular branches ; tbe Tranfuctions, Journals, and Memoirs, of Learred societies, both at bome and abroad; the MS. Lectures of

Eminent Professors on different sciences; and a variety of Original Materials, furnifoed by on Extensive Correspondence.

THE THIRD EDITION, IN EIGHTEEN VOLUMES, GREATLY IMPROVED.

ILLUSTRATED WITH FIVE HUNDRED AND FORTY-TWO COPPERPLATES

VOL. VI.

INDOCTI DISCANT, ET AMENT MEMINISS E PERITI.

E DIN BU R G H.
PRINTED FOR A. BELL AND C. MACFARQUHAR.

MDCCXCVII,

Entered in Stationers Hall in Terms of the act of Parliament.

,

a

a

a

DI A

DI A
Diamond. IAMOND, a genus of earths of the siliceous kind, black; but on closer examination appeared in some Diamond,

called Adamas Gemma by the Latins, Demant parts transparent, and in others charged with foulness,
by the Germans and Swedes, and Diamant by the on which the black hue depended.
French, is the hardest of all stones hitherto discovered; These gems are lamellated, consisting of very thin
commonly clear or transparent; though this property plates like those of talc, but very closely united; the
may perhaps belong only to the crystals, and not to direction of which must be found out by lapidaries be-
the rock from which they originate.' When brought fore they can work them properly: Such as have
to Europe in its rough state, it is either in the form of their foliated substance not in a fat position, are called
roundish pebbles, with shining surfaces, or of octædral by the workmen diamonds of nature.
cryitals; but though they generally appear in octa- The names of oriental and occidental, given by jewel.
dral forms, yet their crystals are frequently irregular, lers to this and all other precious stones, have a differ-
especially when the surface inclines to crystallize du- ent meaning from the obvious sense ; the finett and
ring the thooting of the whole cryftal, and also when hardest being always called oriental, whether they be
several of them unite in one group; in which case the produced in the east or not. Those called occidental
one hinders the other from assuming a regular form. are of inferior value ; but according to Mr Jefferies,
Mr Magellan, however, informs us, that diamonds who has written a treatise on the subject, the diamonds
sometimes assume other forms. He has seen a rough of Brasil equal the finest oriental ones. The art of
diamond in its native state, of a regular cubical form, cutting these gems was invented in 1476 by Louis de
with its angles truncated or cut off; likewise ano- Berquen a native of Bruges in the Austrian Nether-
ther belonging to Dr Combe of London, whose square lands. This stone becomes luminous in the dark, by
fides were naturally joined by two very narrow long fa- exposure during a certain time to the rays of the sun ;
cets, forming angles of about 120 degrees; and the by heating it in a crucible ; by plunging it in boiling
corners were quite perfect.

water; or by rubbing it with a piece of glass. By
Though the diamond is commonly clear and pellu- friction it acquires an electrical property, by which it
cid, yet some of them are met with of a rose colour, attracts the substance used for foils called black maslic,
or inchining to green, blue, or black, and some have and other light matters. The author of the Chemical
black specks. Tavernier saw one in the treasury of Dictionary says, that diamonds are refractory in the
the Mogul, with black specks in it, weighing about fire, and even apyrous. Nevertheless, experiments have
56 carats ; and he informs us, that yellow and black been made, which prove that diamonds are capable of
diamonds are produced in the mines at Carnatica. Mr being dissipated, not only by the collected heat of the
Dutens also relates, that he saw a black diamond at fun, but also by the heat of a furnace. Mr Boyle says,
Vienna in the collection of the prince de Lichten- that he perceived certain acrid and penetrating exha-
stein. Some diamonds have a greenish crust; and of lations from diamonds exposed to fire. A diamond by
these M. Tavernier relates, that they burst into pieces exposure to a concave speculum, the diameter of which
while working into a proper shape, or in the very act was 40 inches, was reduced to an eighth part of its Plilef.
of polishing on the wheel

. In confirmation of this, weight *.
In confirmation of this, weight *. In the Giornale de Letteraii d'Italia, tom.

Tranfire,

n° 386. he mentions a large diamond worth upwards of 5000l. viii. art. 9. we may read a relation of experiments Sterling, which burst into nine pieces while polishing made on precious stones, by order of the grand duke on the wheel at Venice.

of Tuscany, with a burving lens, the diameter of which The finest diamonds are those of a complexion like was two thirds of a Florentine ell, near the focus of that of a drop of pure water. It is likewise a valuable pro- which was placed another smaller lens. By these experty if they are of a regular form and truly made; as periments we find, that diamonds were more altered by also that they be free from stains, spots, specks, flaws, solar heat than most of the other precious stones, aland cross veins. If diamonds are tinctured yellow, though not the leait appearance of a commencing fublue, green, or red, in a high degree, they are next fion was observable. A diamond weighing 30 grains, in efteem; but if they are tin&tured with these colours thus expofed during 30 seconds, loit its colour, luftre, only in a low degree, the value of them is greatly di- and transparency, and became of an opaque white. In minished. There are also diamonds of other com- five minutes, bubbles appeared on its furface; soon afplexions ; such as brown, and those of a dark hue: terwards it burst into pieces, which were dissipated ; the first resembling the browneft sugar-candy, and the and the small fragment which remained was capable of latter dusky iron. In the Philosophical Commerce of being crushed into fine powder by the presiure of the Arts, Dr Lewis tells us of a black diamond that he blade of a knife. Neither the addition of glafi, flints, himself had seen. At a distance, it looked uniformly fulphur, metals, or falt of tartar, prevented this diffiVol. VI. Part I.

А

pation

a

a

« EelmineJätka »