s. 10, to be imported duty-free, excepting a convoy-duty of 7d. per cwt.—It deserves to be remarked, that a small addition of commons It renders the yellow shade darker; sal-ammoniac precipitates an orange-coloured powder, and the super-natant liquid has an aurora yellow appearance. Cloth dyed with this drug, without being previously impregnated with neutral salts, or alkalies, acquire a yellow colour of a brownish shade, which undergoes no change in the air; but M. Berthollet observes, that lustre and vivacity of colour can be obtained only, by preparing the stuffs with the usual solutions.—Pörner, a German chemist of repute, maintains that alum, and solutions of tin, produce indeed a more lively tint, but which easily fades in the open air.
G.
GAD-FLY, or Breeze, Oestrus bovis, L. an insect with spotted wings, and a yellow breast. It has a long proboscis, with a sharp dart, inclosing two others within it.
These insects particularly infest oxen, in the backs of which they deposit their eggs, and where the maggots are nourished in the winter, till the month of June: during the whole summer, they plague the cattle by means of their darts to such a degree, that the distressed animals are induced to rush into the water for refuge, till night approaches.—We believe that the washing of oxen and cows, in the early spring with a decoction of tobacco, or any other bitter and acrid plant, would greatly tend to prevent the generation of these vermin.
Gad-flies are also very destructive to flowers and trees, the juices of which they absorb; and likewise injure the roots of trees, which, if not timely prevented, they gnaw so severely, that the stem will languish, and at length perish. The only remedy hitherto discovered is, to dig up the soil at the root of such flowers or trees, to kill the insects; and to lay on fresh earth; by which means the plants will be speedily recovered, if they have not been too long neglected.
GALBANUM, a gum that exudes from the stem of the Bubon gummiferum, L. or Gum-bearing Macedonian Parsley, a native of Persia and different parts of Africa.—The concrete juice is semi-pellucid, soft, and tenacious; of a yellowish-red colour; a strong smell; and a bitterish nauseous taste. The best sort is imported in pale-coloured masses, which, when opened, apparently consist of clear white tears.—This gum is of an emollient and resolvent nature; a tincture prepared of half an ounce of it, dissolved in eight ounces of proof spirit, of which one spoonful is taken every two hours, has been found serviceable in chronic asthmas, and inveterate coughs, where expectation required to be supported. It is chiefly employed externally, in white swellings, as well as obstructions of the abdomen, and frequently in the form of a plaster, though it is more efficacious in a liquid state.—In hysteric spasms, and inflamed hemorrhoids, we are
