five or six feet in diameter in the middle, and two feet and a half at the month or superior part The walls
are about a foot and a half in thiekness. To about two-thirds of the height these are constructed with freestone,
hut above that with oven-earth. When the ovens are finished, and quite dry and tight bundles or
laggots of the wood, tied up with hazel or vine rind, are set upright on the grating; the ligature is cm by
means of a blade fixed at. the end of a stick; and the pieces are spread about, the interstices being filled with
chips. I his first layer being properly made, a second fiiggot is let down, then a third, and so on until the
oven is full, as high as the hand can reach, when chips and shavings are laid on, to the thickness of three or
lour inches, and the mouth is covered up with flat stones piled one upon another so as to close all caps except
at the center, where an opening is left four or five inches in diameter. All things being thus prepared the
chips at the top are set on fire, and the operators, who from experience are enabled to ascertain when the
materials are sufficiently kindled, seize the proper time to shut up the mouth entirely with a flat stone- and
they stop up with earth every interstice from which smoke is seen to escape. The wood then becomes reduced
to charcoal, and the resinous part of it, mixed with the sap, flows through the grate down into the cavity
at the bottom of the oven. When this cavity is full up to the place where the iron tube is fixed the tar flows
into barrels placed to receive it. It is from custom alone that the persons who superintend the operation
ascertain when the wood has given out all its resinous liquor; they then open the top of the oven removing
the stones, and collecting the soot which lodges in their interstices as well as on the sides of the oven and
which forms a kind of lamp-black; lastly, they take out the charcoal that has lodged on the gratin'/ and
recommence the operation by laying on wood as before. Such impurities as are heavier than the tar with
wind, they were mixed, remain on the stone that serves as a floor to the oven, whilst the tar itself flows on
the surface through the tube, which, as we have remarked before, is five or six inches above the level of the
stone. As far as we can judge, all the art of the operation consists in a proper management of the fire for
f lie oven be too closely stopper , the fire is extinguished, the wood is but imperfectly charred, and ver/
little tar is extracted; but it, on the contrary, the wood burn too briskly, a "real pronorlion of ll • Y
matter is consumed. When the fire is properly regulated, there is no flame in the oven; the heat J Z T
vyhich are reverberated on the wood, cause the resin and sap to flow from the latter together It wool 1
that a more certain mode of regulating the heat would be, instead of closin'* the ton ! f the oven wit!
and turf, to adapt registers of different sizes to a kind of dome, which might form the upper part of it Tnd
renclei the structure more neat and commodious. ^ ’
Tar has been used as a medicine both externally and internally. The ancients had a hio-h opinion of its
efficacy m pulmonary diseases, supposing it to promote expectoration, relieve dyspnma, and chelTpitting f
blood. Dioscorides particularly speaks of its utility in these cases. He also recommend it i I P ,■ f
eais, throat, or other internal parts.' In fact, there is no end tn the • , y> r m the
on the properties of tar, which, if we are to give credit to all the accounts g iv e n t fT is L^aNoth™*6"
of all the maladies of the human frame. The colleges of London and Edinburgh direct« to lie m a J ' T "
ointment (Unguenturn. PicisJ; the former, by means of the admixture r f ° l - to an
........... » • -« « .. yellow w „ ’ This o l l l t T w i : 7 ™
TAR-WATER.
( Itifusum Picis liquidée pinece.)
Aqua picea. Pharm, paup.
Watee impregnated with the more soluble parts of tar, and hence called Tar Water
popular remedy for various obstinate complaint" both acute and chronfr I t w^ m ^ t l d T h “ ^
reputation principally to the celebrated Dr. George Berkeley, Bishop of Cloyne, who wrote a long d C
See also Pliny, lib. 24. c. 7 .
Ä
7 3
tation on it, under the title of “ Sim, or a chain o f philosophical reflexions and enquiries concerning the virtues of
Tar Water. ’ A narrative of its success, with a great number of cases and remarks, was published also by
Thomas Prior, Esq. From the accounts given by these writers and by Cullen, (who appears to have entertained
no mean opinion of its efficacy) it appears to strengthen the lone of the stomach, to excite appetite,
promote digestion, and remove many dyspeptic symptoms, at the same time increasing the excretions, particularly
that of urine. Cullen believed the virtues of this medicine to depend chiefly on the acid principle it
contains, and it was on this account that the Bishop of Cloyne preferred the Norway Tar (made from Finns
Abies) to that of New England; this acid, however, does not appear to differ from that which is extricated
by fire from all kinds of recent wood.' The proportions recommended by the Bishop arc a gallon of cold
water to a quart of tar; these are to be mixed thoroughly by means of a ladle or flat stick, with which the
liquor is to be stirred for the space of three or four minutes; and the vessel containing it must stand forty-
eight hours, that the tar may have time to subside; the former is then strained. Tar water distilled yields
a liquor much impregnated with its flavour, though more grateful than the infusion itself both in smell and
taste. There remains a light, spongy, blackish matter, not acid, but bitter, partially soluble again in water.
^Whatever commendation tar-water may formerly have had, or may justly be entitled to, it does not receive
"much in the present day, being but little used, on account of other medicines appearing to possess the same
properties in a more exalted degree; and indeed there are other terebinthinate preparations better suited than
this to answer the purposes for which it was formerly recommended, as will be mentioned in the course of
this dissertation.
P I T C H.
(Pix pinea inspissata)
Boo-xaç, o f the Greeks. Spissa Pix. Pliny.
Brai-gras, of the French.
T h e usual mode of making pitch consists in melting coarse hard resin (or brai-sec, as it is called in France)
with an equal quantity of tar, in large copper vessels similar to those used for boiling the raw juice. If the
tar be too thin, the proportion of resin is increased; and, on the other hand, if it be thick, a third part of
tar is sufficient. Should the process of inspissation be carried to its utmost limit, the pitch becomes quite
haul and dry, and is called in the shops Pix arida (the n a n d natyoriova of the Greek writers), which
is less pungent and less bitter than the common tar, and is used only in some external applications, as an
adhesive substance agreeing in its medicinal virtues with the common digestives.
When melted with oils, resins, and fats into ointments and plasters, pitch is said to be very apt to separate
and precipitate. Dioscorides describes the best pitch as being shining, odorous, gummy, and of a reddish
black colour, which were the qualities of the Lycian and Calabrian pitch.' It was prescribed by him, and
also by Celsns, as a proper ingredient in plasters for maturing abscesses and healing wounds.
Pitch was much employed by the ancients for giving flavour and fragrance to their wines, which were also
supposed to acquire from it useful medicinal properties, as we have before remarked, when speaking of the
properties ol terebinthinate substances in general. Their mode of pitching casks and other vessels is
described by Columella. We are told by Pliny ol a preparation of tar with vinegar, called Brutia, which
was employed for the same purposes;' and this author says that it was usual to sprinkle the first ferment of
new wine, or mustum, with powdered resin.
In boiling down tar to dryness without addition, there comes over an acid liquor in considerable quantity,
and also an ethereal oil, which seems to differ from the oil of turpentine only in being impregnated with an
empyreumatic quality; it was called by the ancients Oleum Picinum. The medicinal properties of this oil are
similar to those of tar.*
1 he extensive use of pitch and tar in ship-building is too well known to require particular mention. A
mixture of pitch and wax, by which crevices in vessels are rendered impermeable to water, was called by the
’ Lewis’s Mat. Med. Art. Pix liquida. “ See page 2.
z Dioscorid. Lib. 1 . c
1 De re rustica.” Lib. 12. c. 18.
M fM H fS
2 P