This section is from the book "An Experimental History Of The Materia Medica", by William Lewis.
Opobalsamum or Balsam of Gilead: a re-sinous juice, obtained from an evergreen tree or shrub (balfamum fyriacum rutae folio C. B.J said to grow in Arabia. The belt sort, which naturally exudes from the plant, is scarce known in Europe; and the inferiour kinds, said to be extracted by lightly boiling the branches and leaves in water, are very rarely seen among us.
The true opobalsam, according to Prosper Alpinus, is at first turbid and white, of a very strong pungent smell, like that of turpentine; but much sweeter and more fragrant, and of a bitter, acrid, astringent taste: on being kept for some time, it becomes thin, limpid, light, of a greenish hue, and then of a gold yellow, after which it grows thick like turpentine, and loses much of its fragrance (a). Some resem-ble the smell of this balsam to that of citrons, others to that of a mixture of rosemary and fage flowers. I have sometimes met with a curious balsam of this last kind of smell, exceedingly fragrant, limpid, and thin: dropt on water, it spread itself all over the surface, imparting to the liquor a considerable share of its taste and smell: the grosser part, that remained on the top of the water, was so tenacious, as to be easily taken up at once with the point of a needle, which is reckoned, by Alpinus and others, as a characteriftic of the true balsam.
This precious balsam is of great esteem in the eastern countries, both as a medicine, and as an odoriferous unguent and cosmetic. Its great scarcity has prevented its coming into use among us: nor are its virtues, probably, supe-riour to those of some of the refinous juices more common in the shops; all these substances being in their general qualities alike, though differing in the degree of their gratefulness, pungency, and warmth.