GUA 



GUA 



r<kmd, of a deep brownish-yellow colour, 

 and of the size of common shot : on the 

 approach of winter, or any great change 

 of weather, these insects are said to re- 

 move the nest, by sinking it deeper, so as 

 to secure it from the power of frost ; and, 

 when the spring commences again, raising 

 it in proportion to the warmth of the sea- 

 son, till at length it is brought so near the 

 surface as to receive the full influence of 

 the air and sun-shine; but should unfa- 

 vourable weather again take place, they 

 again sink the precious_deposit, and thus 

 preserve it from danger. The young at 

 their first exclusion are about the size of 

 ants, for which, on a cursory view, they 

 might be mistaken ; but on a close in- 

 spection are easily known by their broad 

 feet, &c. In about the space of a month 

 they are grown to the length of more 

 tkan a quarter of an inch ; in two months, 

 upwards of three quarters; and in three 

 months, to the length of more than an 

 inch. Of this length they are usually seen 

 during the close of autumn, after which 

 they retire deep beneath the surface, not 

 appearing again till the ensuing spring. 

 During their grov^th they cast their skin 

 three or four times. The mole-cricket 

 lives entirely on vegetables, devouring 

 the young roots of grasses, corn, and va- 

 rious esculent plants, and commits great 

 devastation in gardens. It inhabits 

 Europe and America. 



GUAIACUM, in botany, a genus of the 

 Decandria Monogynia class and order. 

 Natural order of Gruinales. Rutaceze, 

 Jussieu. Essential character : calyx five- 

 cleft, unequal ; petals Jive, inserted into 

 the receptacle ; capsule angular, five- 

 celled. There are four species. From 

 the G. officinale is obtained a resin, which 

 exudes spontaneously, and is also driven 

 out artificially by means of heat. This 

 substance has been long known and cele- 

 brated as a medicine in various cases ; and 

 in the Transactions of the Royal Society 

 for the year 1806, we have a very com- 

 plete analysis of it : by distillation 100 

 parts yielded, 



Acidulous water - - - 5.5 

 Thick brown oil - - - 24.5 

 Thin empyreumatic oil - 29.0 



Charcoal 30.5 



Gases consisting of carbo-"> 

 nic acid and carbureted > 10.5 

 hydrogen - - - - j 



100.0 



Hence it is inferred, that guaiacum 

 agrees in many respects with the resins, 

 but it differs from them, 1. in the quanti- 



ty of charcoal it leaves when distilled in 

 close vessels ; 2. in the action that nitric 

 acid has upon it ; and, 3. in the changes 

 of colour that it undergoes when its solu- 

 tions are treated with nitric and oxymu- 

 riated acids. Its properties may be thus 

 enumerated : it is a solid substance re- 

 sembling a resin; its colour varies, but 

 is generally greenish ; it is readily dis- 

 solved in alcohol; alkaline solutions dis- 

 solve it with ease : most of the acids act 

 upon it with considerable energy ; if di- 

 gested in water, a portion is dissolved, 

 the water acquiring a greenish-brown co- 

 lour : the liquid, being evaporated, leaves 

 a brown substance, which possesses the 

 properties of an extract, being soluble in 

 hot water and alcohol, but scarcely at all 

 in sulphuric ether, and forming precipi- 

 tates with the muriates of alumina, tin, 

 and silver. 



GUANA. SeeLAcERTA. 



GUANO, a substance found on many 

 of the small islands in the South "Sea, 

 which are the resort of numerous flocks 

 of birds, particularly of the Ardea and 

 Phsenicopterus genus. It is dug from 

 beds fifty or sixty feet thick, and used as 

 a valuable marmre in Peru, chiefly for In- 

 dian corn. It is of a dirty yellow colour, 

 nearly insipid to the taste, but has a pow- 

 erful smell, partaking of castor and vale- 

 rian. According to the analysis of Four- 

 croy and Vauquelin, about one-fourth of 

 it is uric acid, partly saturated with am- 

 monia and lime. It contains likewise ox- 

 alic acid, partly saturated with ammonia 

 and potash ; phosphoric acid, combined 

 with the same bases and with lime; small 

 quantities of sulphate and muriate of pot- 

 ash and ammonia ; a small portion of fat 

 matter; and sand, partly quartzose, partly 

 ferruginous. 



GUARD, in a general sense, signifies 

 the defence or preservation of any 'thing; 

 the act of observing what passes, in order 

 to prevent surprise; or the care, precau- 

 tion, and attention we make use of, to pre- 

 vent any thing happening contrary to our 

 intention or inclinations. 



GUARD, in the military art, is a duty 

 performed by a body of men, to secure 

 an army or place from being surprised by 

 an enemy. 



In a garrison the guards are relieved 

 every day, and it comes to every soldier's 

 turn once in three days, so that they have 

 two nights in bed, and one upon guard. 

 To be upon guard, to mount the guard, 

 to dismount the guard, to relieve the 

 guard, to change the guard, the officer of 

 the guard, or the Serjeant of the guard, 



