AIRING. 



ALBURNUM. 



to that of the Aira Jlexuosa, differing only in 

 having less bitter extractive matter and of 

 more tasteless mucilage ; but the soft hairy 

 foliage of the grass appears at once the cause 

 of this dislike in cattle to eat it. It flowers 

 about the first week in July, and the seed is 

 ripe about the beginning of August. 



Aira Jlexuosa. Zig-zag hair-grass ; wavy 

 mountain hair-grass. The Aira Jlexuosa is 

 much more productive on its natural soil than 

 the Festuca ovina , but it requires a deeper soil 

 though not a richer. The Festuca ovina is 

 more common among heath, the Aira Jlexuosa 

 among furze, though both grasses frequently 

 grow intermixed on the same soil. To those 

 who attempt the improvement of such soils in 



a secondary manner only, this species of hair- 

 grass appears to be the best of those grasses 

 natural to the soils in question, and may form 

 a principal part of a mixture of seeds for that 

 purpose of improvement. The produce of 

 this grass on a heath soil is superior to that 

 on a clayey loam in the proportion of 2 to 1. 

 The proportional value in which the grass at 

 the time of flowering exceeds that of the latter- 

 math, is as 8 to 7. Flowers in the first week 

 of July. Seed ripens in August. 



In England the proportionate value of the 

 different varieties of Aira as deduced from ex- 

 periments may be ascertained by reference to 

 the following classified table of results : 



AIRING. In the management of horses, 

 implies the exercising them in the open air, 

 which is of the greatest advantage to them 

 when performed with moderation, and accord- 

 ing to the circumstances or state in which they 

 are in respect to their health and the nature 

 of their keep. By this means their legs are 

 prevented from swelling, their stomachs im- 

 proved, and their wind rendered more free and 

 perfect 



AIR VESSELS, of vegetables, are certain 

 horizontal vessels of large diameter, that pass 

 through the bark of trees to the alburnum, [or 

 white internal bark.] These horizontal vessels 

 Dr. Darwin supposes to contain air, enclosed 

 in a thin moist membrane, which may serve 

 the purpose of oxygenating the fluid in the ex- 

 tremities of some fine arteries of the embryo 

 buds, in the same manner as the air at the 

 broad end of the egg is believed to oxygenate 

 the fluids in the terminations of the placental 

 vessels of the embryo chicken. 



ALBUMEN is the name given by chemists 

 to the impure glossy viscid liquid, which forms 

 the white of an egg. This white is composed 

 chiefly of albumen mixed with some mucus, 

 soda, and sulphur. 



Albumen unites readily with water, and 

 when heated to 165 it coagulates into a white 

 solid mass ; but when mixed with ten times 

 its weight of water, it no longer is coagulated 

 by heat. It is composed, according to the 

 analysis of MM. Gay Lussac and Thenard, of 



Carbon 52-883 



Oxygen ...... 23872 



Hydrogen 7-540 



Azote 15-705 



(Rech. Phys. Chem. ii. 332.) lOO'OOO 



Albumen (which is nearly identical in com- 

 position with the gluten of vegetables), is one 

 of the most important and common of all the 

 animal substances. It abounds in bones, mus- 

 8 



(Sinclair's //or/. Gram. Wob.) 



cle, the membrane of shells, sponges, &c.; 

 and, according to the experiments of Hatchett, 

 cartilage, nails, horns, hair, &c., are almost 

 entirely composed of it. (Thomson, vol. iv. 

 p. 407.) 



ALBURNUM. An integument composed 

 of a soft white substance, scarcely perceptible 

 in some sorts of trees, situated between the 

 liber and the wood. In the oak and elm it is 

 hard and very conspicuous. It is as it were 

 an imperfect wood, not having acquired that 

 state of consistence necessary to perfect wood ; 

 hence it may be compared to the cartilage in 

 animals, which at length becomes bone. This 

 state must necessarily be passed through be- 

 fore wood can be formed. The hardness of 

 this substance is in proportion to the vigour 

 of the plant or tree. 



The vessels of the alburnum in their living 

 state possess the property of conveying the 

 sap-juice, which is propelled upwards in the 

 early spring, by the absorbent terminations 

 of the roots, as visible in decorticated oaks, 

 the branches of which expand their buds like 

 those of the birch and vine in the bleeding 

 season. That the vessels of the alburnum in 

 their living state occasionally act as capillary 

 syphons, through which the sap-juice is first 

 pushed upwards by the absorbent extremities 

 of the roots, and afterwards returns down- 

 wards, partly by its gravitation, in branches 

 bent below the horizon, appears from an ex- 

 periment of Dr. Walker ; and lastly, that the 

 vessels of the alburnum, after their vegetable 

 life is extinct, possess a power of capillary at- 

 traction of the sap-juice, or of permitting it to- 

 pass through them occasionally, appears from 

 the following experiment : A branch of a 

 young apple-tree was so cankered, that the 

 bark for about an inch round it was totally 

 destroyed. To prevent the alburnum from 

 becoming too dry by exhalation, this decayed 



57 



