Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/99

LEA tiie skins be compressed in certain heavy rollers, after being previous- ly immersed in beef-fat, or oil. The additional greasing", and pressing, will not greatly increase the price of sole-leather ; which, after being a whole year in tanning, imbibes water in a much smaller proportion than cow-leather, when dressed with fat. — We regret that our li- mits do not permit us to specify the very ingenious experiments made by M. de St. Real ; as we are convinced they will contribute to improve the art of tanning. Anoti^er method of preventing leather from being penetrated by water, consists in exposing it with the riesh-side towards the tire : af- ter which, a coat of warmed tar is to be applied with a proper brush, three or four times successively, according to the thickness of the leather, till the liquid matter pene- trate through the whole skin. The durability and stre;igth of shoes, &c. will be considerably increased, if, in laying on the last coat of tar, they be sprinkled over with a small quantity of tine iron-filings, which will, in a manner, fill up the pores of liie leather. Lastly, shoes may be rendered impermeable to mois- ture, by occasionally rubbing the «oles with hot tar: thus the feet may be preserved diy and A^armj an important objed in this climate, especially during the winfer season. Various ads of parliament i^ave been parsed, relative to die dressing, bringing of leather to market, &c. for the greater convenience uf trade, and to prevent frau'.iulent pra£tices ; but, as they relate wholly to curriers, tanners, and leather- cutters, we shall not enter into detail respefting them. — This arti- cle pays at present, on importation, tiie prohibitory duty of S-li. 14*. LEA [St percent, according to its value; and is entitled only to a drawback of 25 per cent, on being again ex- ported. LEAVEN, strivSUy sigriifies sour- dough, which acquires its acidity, when preserved after kneading flour with yeast, in order to fer- ment a larger quantity of paste. — ^ It is a very imperfect substitute for yeasl ; and, as it communicates to the bread an astringent taste which few persons rehsh, it ought to be used only where barm cannot be procured. As, however, the lat- ter ferment is sometimes difficult to be obtained, especially during the winter, we shall communicate the most simple methods of pre- paring as well as of preserving it, under the article Yeast. LEAVES, in botany, are de- fined by LiNNiEus to be the organs of motion, or muscles of a plant : according to Dr. Darwin, they constitute the lungs of each indivi- dual bud. — See Eud. Leaves are of a deeper green co- lour than the foot-stalks on which they stand; being formed by the expansion of the vessels of such stalks that produce several ramifi- cations 3 mutually intersecting each other, and thus making a kind of net ; the meshes of which are fill- ed up with a tender porous sub-" stance, variously called the pulp, pifli, or parenchyma. This net is provided, chiefly on the surface of the leaf, witi; a great number of porous or absorbent vessels, which are destined to imbibe the humidity of the air. The upper surface serves as a defence to the lower j and so essential is this disposition to the vegetable economy, that, if a branch be inverted so as to de- stroy the natural direftion of the leaves, these in a short time will a spon-