GLOW-WORM. 



GNATS. 



or marsh samphire (8. herbacea), is an annual 

 plant, with a small fibrous root, a bushy, green 

 stem a foot high, with opposite branches ; 

 woody centre very tough. Flowers on nu- 

 merous short-jointed spikes. The whole plant 

 has a saline taste, abounding in salt juices, and 

 is therefore devoured with avidity by all kinds 

 of cattle ; and it is a very wholesome food, 

 especially for sheep. It is often pickled, as a 

 substitute for the very different strongly aro- 

 matic rock samphire (CrUhmitm murin/nnni), to 

 which it is for this purpose very little inferior. 



Several other species of glass-wort are enu- 

 merated, three of which Mr. Xuttall gives as 

 American, which, like the European, affords 

 soda when burned, and are preserved in vine- 

 gar as a pickle. 



s,.da is yielded in large quantities by the 

 ashes of the different species of Snlimnii-i : ;i\i<\ 

 is in great request for manufacturing soap and 

 glass: the best is imported from Spain, under 

 the name of Barilla (see SODA). These plants 

 will grow in any common soil, and are readily 

 increased by divisions. Being natives of the 

 sea-shore, the plants will thrive better if a little 

 salt be occasionally sprinkled on the surface 

 of the soil. (H17/i/'v f y.) 



GLOW-WORM (Lniiifnjris ././/). This 

 insect is remarkable for the light it emits dur- 

 ing the night. Tins luminous appearance de- 

 pends upon a phosphorescent fluid found at 

 the lower extremity of the inject; which, by 

 unfolding or contracting itself, it can withdraw 

 at pleasure ; a power of consequence to the in- 

 sect, as it is thus secured from the attacks of 

 nocturnal birds. The light arises from a sac, 

 which is diaphanous, and contains a secreted 

 fluid consisting of albumen and phosphorus. 

 Glow-worms are sometimes called St. John's 

 worniN. from appearing first as a common oc- 

 currence about the Feast of St. John the Bap- 

 tist. Thr glow-worm is the perfect female of 

 a winded beetle; the malt-s ilv about chiefly in 

 autumn, and frequent the grassy plantations of 

 juniper trees. 



GLUE (Lat. gluten), is prepared from the 

 chippings of hides, hoofs, &c. The refuse 

 matter of the glue-makers, according to Mr. 

 Miles, is an excellent manure for turnips. 



GLUTEN (Lat.). The viscid elastic sub- 

 stance which remains when wheat flour is 

 wrapt in a coarse cloth, and washed under a 

 stream of water, so as to carry off the starch 

 and soluble matters. Gluten, when pure, is 

 inodorous, insipid, tenacious, adhesive, and 

 elastic. It is insoluble in water, but soluble in 

 hot alcohol. It is also soluble in a dilute so- 

 .ution of potash. When kept moist and warm, 

 it ferments. Gluten exists in grains, and oc- 

 casionally in other parts of vegetables ; but it 

 is a characteristic ingredient in wheat, giving 

 wheat flour its particular toughness and tena- 

 city, which particularly fits it for the manufac- 

 ture of bread, and for viscid pastes, such as 

 macaroni and vermicelli. There is generally 

 more gluten in the wheat of warm climates 

 than of cold; hence the excellence of that 

 grown in the south of Europe for the manu- 

 factures just mentioned. Gluten seems also 

 to constitute the essential part of yeast. Its 

 uses as a varnish, a ground for paint, &c., 



pointed out by Cadet, likewise deserve atten- 

 tion. Gluten was discovered in 1742 by Bee- 

 caria. an Italian philosopher, to whom we are 

 indebted for the first analysis of wheat flour. 

 The number of plants containing gluten is 

 very considerable. Proust found it in acorns, 

 chestnuts, rice, barley, rye, peas and beans, 

 and in apples and quinces. He found it also 

 in the leaves of the cabbage, cress, hemlock, 

 borage, saffron, &c., and in the sedums ; in the 

 berries of the elder, the grape, &c. ; in the pe- 

 tals of the rose, &c. Gluten has been shown 

 to resemble albumen so closely that they can 

 hardly be considered as distinct principles. 

 Gluten contains nitrogen, and has, conse- 

 quently, been called the vegeto-animal princi- 

 ple, on this account. It yields ammonia, when 

 subjected to destructive distillation ; and the 

 vegetables which contain it give out a pecu- 

 liarly disagreeable odour during their putre- 

 faction. M. Magendie^ after feeding animals 

 upon different kinds of food, states that gela- 

 tine, fibrin, albumen, when taken singly, do not 

 the power of nourishing animals for 

 any length of time; they always die. The 

 reverse is the case, however, with gluten, upon 

 which animals thrive well and long. 



<i\ \Ts '(,'. r, Linn.). A genus of insects 

 comprising several species, which are well 

 known by the severe punctures they inflict. 

 The gnat most common in Europe is the C. 

 pipiens, so naim-d from the sound which it 

 emits in its flight. The stint,' consists of 5 

 pieces and a sheath ; some of the pieces are 

 simple lancets ; others are barbed, and act 

 both as piercers ami as siphons, to extract the 

 blood from tho wounds which they make. 

 Gnats deposit their eggs, to the number of 200 

 by each female, on stagnant waters, where 

 they are hatched into small grubs in the course 

 of 2 or 3 days. On the sides are 4 small fins, 

 by the aid of which the insect swims about, 

 and swiftly dives to the bottom. The larva re- 

 tains its form a fortnight or 3 weeks, when it 

 is converted into the chrysalis, in which state 

 it continues 3 or 4 days, floating on the surface 

 of the ^ter, till it assumes the form of the 

 gnat. The most efficacious remedies for their 

 sting are olive oil, unsalted butter, or fresh 

 hog's lard, timely rubbed in. Gnats have 

 occasionally appeared in such numbers as 

 to form a cloud, almost darkening the air, 

 as was the case in August, 1766, near Oxford. 

 Spencer describes a similar flight of them in 

 Ireland 



"As when a swarme of gnats at eventide, 



Out of the fennes of Allan doe arise, 

 Their murmuring small trumpets sownden wide, 

 Whiles in the air their clustering army flies, 

 That as a cloud doth seem to dim the skies." 



Faery Queene. 



The mosquito of tropical climates is a spe- 

 cies of the same genus as the gnat ; and the 

 latter is not less troublesome in some of our 

 marshy districts than the mosquito in the West 

 Indies. In the marsh land of Norfolk, the bet 

 ter classes are forced to have gauze curtains to 

 keep them off during the night. 



The species of gnat best known in America 



is a small, black fly, which swarms during the 



month of June, and is especially annoying to 



travellers, and the first inhabitants of new set- 



2 Z 54) 



