GALLIC ACID. 



water, into which they instinctively enter. 

 Hence Virgil, describing this, says : 



"The universal herds in terror fly; 

 Their lowings shake the woods and shake the sky." 



Humboldt mentions a species of CEstrus which 

 is found in the low regions of the torrid zone, 

 and has been named Oestrus hominis, from its 

 attacking man, and depositing its eggs in his 

 skin, causing there painful tumours. (La Geog. 

 des Plantes, p. 186.) 



Of the large Gad-flies, or Horse-flies found in 

 America, one of the most common is of a black 

 colour, having its back covered with a whitish 

 dust or bloom, like a plum. The eyes are very 

 large, and almost meet on the top of the head ; 

 they are of a shining purple-black or bronzed 

 black colour, with a narrow, deep black band 

 across the middle, and a broad band of the 

 same hue on the lower part. The body of this 

 fly is seven-eighths of an inch or more in 

 length, and the wings expand nearly two 

 inches. The Tabanus dnctus, of Fabricius, or 

 orange-belted horse-fly, is not so common, and 

 is rather smaller. It is also black, except the 

 first three rings of the hind-body, which are 

 orange-coloured. The most common of our 

 smaller horse-flies is the Tabanus lincola, so 

 named by Fabricius, because it has a whitish 

 line along the top of the hind-body. Besides 

 these flies, we have several more kinds of Ta- 

 banus, some of which do not appear to have 

 been described. These blood-thirsty insects 

 begin to appear towards the end of June, and 

 continue through the summer, sorely torment- 

 ing both horses and cattle with their sharp 

 bites. Their proboscis, though not usually 

 very long, is armed with six stiff, and exceed- 

 ingly sharp needles, wherewith they easily 

 pierce through the toughest, hide. It is stated 

 that they will not touch a horse whose back 

 has been well washed with a strong decoction 

 of walnut leaves. The eyes of these flies are 

 very beautiful, and vary in their colours and 

 markings in the different species. 



The golden-eyed forest flies are also distin- 

 guished for the brilliancy of their spotted eyes, 

 and for their clouded or banded wings. They 

 are much smaller than the horse-flies, but re- 

 semble them in their habits. Some of them 

 are entirely black (Chrysops ferrugatus, Fabri- 

 cius), others are striped with black and yellow 

 (Chrysops vittatus, Wiedemann). They fre- 

 quent woods and thickets, in July and August. 

 (Harris.) 



GALLIC ACID. An acid obtained from 

 galls and several other vegetable astringents, 

 chiefly from the bark. The following table 

 will serve to show the proportions of this acid 

 in different plants : 



tot* 



. 9 



Willow trunk - 

 Oak, cut in winter 

 Willow (boughs) 

 Plum tree 

 Cherry tree 

 Sallow 



Mountain ash 

 Poplar 

 Elm 

 Beech 

 Sycamore 

 Birch 

 Elder 



But although the above-named barks yield 

 514 



each 8 



each 7 



each 4 



GALLOP. 



the quantities of gallic acid mentioned, yet it 

 is uncertain whether they actually contain any 

 ready formed. Gallic acid is procured bv ex- 

 posing the. decoctions of galls, or of any astrin- 

 gent bark, to the air, until it becomes mouldy, 

 and the tannic acid attracts the oxygen of the 

 air, and is converted into the gallic acid. In 

 this state the acid forms in crystals, mixed 

 with crystals of another acid, the cllagic, which 

 are easily separated from it, being insoluble in 

 water. 



Pure gallic acid has a weak, sour, astringent 

 taste. It is soluble in 100 parts of cold water, 

 and forms an ink with solution of green vitriol 

 (sulphate of iron). It is distinguished from 

 tannic acid, which is ready formed in astrin- 

 gent barks, by not precipitating solution of 

 glue. It is a powerful astringent, and may be 

 administered in doses of two or three grains in 

 internal bleedings. 



GALLINACEOUS FOWLS. One of the 

 two divisions of domestic poultry reared in 

 Europe, comprehending, among others, the 

 common cock and hen, the turkey, the guinea- 

 fowl, the peacock, and the pigeon. 



GALL FLIES. See FRUIT MAO.OOTS. 



GALL NUTS (Fr.gallis,-lt.gallc"). Excres- 

 cences produced by the Cynips, or Diplolepsis 

 galla tinctorice, a small insect which deposits its 

 eggs in the tender shoots of the Qutrcus infccto- 

 ria, a species of oak abundant in Asia Minor, 

 &c. When the maggot is hatched, it feeds on 

 the morbid excrescence formed by the irrita- 

 tion of the deposited ovum on the surrounding 

 parts, and ultimately, when perfected as the 

 fly, it eats its way out of the nidus thus formed. 

 Good gall nuts are of a bluish-green hue, 

 heavy, and break with a flinty fracture. When 

 they are white, light, with a hole in one side, 

 they are useless. Gall nuts are employed in 

 dyeing, and in medicine. 



GALLON. An English measure of capacity, 

 containing 4 quarts. By act of parliament the 

 imperial gallon is to contain 10 Ibs. avoirdu- 

 pois of distilled water weighed at the tempe- 

 rature of 62 of Fahrenheit, and the barometer 

 standing at 30 inches. This is equivalent to 

 277-274 cubic inches. The old English gallon, 

 wine measure, contained 231 cubic inches, 

 and held 8 Ibs. avoirdupois of pure water; ale 

 and beer measure, 282 cubic inches, and held 

 10 Ibs. 3 oz. avoirdupois of water; and the 

 gallon for corn, meal, &c., 272 cubic inches, 

 containing 9 Ibs. 13 oz. of pure water. Hence 

 the English imperial gallon is about j larger 

 than the old wine gallon, and about W 1 - less than 

 the old ale gallon. See WEIGHTS AND MEA- 

 SURES. 



GALLOP. In horsemanship, a well-known 

 pace to which horses are trained, and of which 

 many kinds are enumerated, but two only are 

 worthy of regard, namely the hand gallop and 

 the full gallop. And these distinctions are 

 founded on the different degrees of velocity in 

 which the animal is impelled, rather than on 

 any peculiarity in the pace itself. In the gal- 

 lop, the horse leads with one fore-leg some- 

 what advanced, but not so much beyond the 

 other, as happens in the canter; and, when he 

 is urged to his utmost speed, his legs are al- 

 most equally placed. The fleetest horses 



