73 - 



t^tion on it, under the title of" Skis, or a chain of philosophical reflexions ami enquiries concerning tlie virtues of 

 lar Water. A narrative of its success, with a great number of cases and remarks, was published also by 

 homas Prior, Esq. From the accounts given by these writers and by CuUeu, (who appears to have enter- 

 tained no mean opinion of its efficacy) it appears to strengthen the tone of the stomach, to excite appetite, 

 promote digestion, and remove many dyspeptic symptoms, at the same time increasing the excretions, parti- 

 cularly 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 Pinus 

 Ahcs) 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 are a gallon of cold 

 ^vater to a cpiart of tar; these are to be mixed thoroughly by means of a ladle or flht 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 liqu6r 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 dissoi'tation. 



PITCH 



\ 



CPioj pinea inspissata) 



Eo(r«af, of the Greehs. Spissa Piw. Pliny, 



Brai-gras, of the French. 



' The usual mode of making pitch consists in melting coarse hard resin (or hrai-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 

 hard and dry, and is called in the shops Pix arida (the n/ro-a ^jj^a, and nci>.i[i7n(rira 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 Celsus, 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 of terebinthinate substances in general." Their mode of pitching casks and other vessels is 

 described by Columella.' We are told by Pliny of 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 boibng 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.^ 



The extensive use of pitch and tar in ship-building is too Avell 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. Phliquida. ' Lib. I. c. 81. 



- ^ Lib. 16. cap. n. 



" See page 2. 

 Dioscoiid. Lib. 1. c. 79. 



X (( Dq j,^ rustical Lib. 12. c. 18. 



2 P 



n 



