lOD 



IRO 



INULIN. A variety of starch. 

 It is coloured yellow by iodine. For- 

 mula, C54 H21 Oj|. — (Parnci) 



INUNDATION OF LANDS. 

 Fields are sometimes covered with 

 water in agriculture, especially mead- 

 ows, and in the cultivation of rice. 

 The water is let in by sluices, and 

 allowed to remain for several days 

 or weeks, and, in meadows, during 

 the whole winter. It kills tliose 

 weeds which are not aquatic, serves 

 to manure the soil, and, in the case 

 of meadows, advances the grass by 

 some weeks, the water protecting it 

 from frost. The lands should be well 

 drained, or on a porous soil ; other- 

 wise the water, sinking, will stag- 

 nate, and become injurious ; it should 

 be perfectly let out by numerous 

 drains. By this practice, meadows 

 have been rendered fertile without 

 other manure for ages. The sedi- 

 ment deposited is sometimes called 

 icarp, and the inundation warping. 



INVERTEBRATE ANIMALS, 

 INVERTEBRAT-^. Animals with- 

 out an internal skeleton or back bone 

 (vertebral column), such as crabs 

 {crustaceans), insects {articulata), or 

 shell-fish (molluscans), &c. 



IN VO LUC EL, INVOLUCEL- 

 LUM. A small or partial involu- 

 crum surrounding the secondary um- 

 bels, &c. 



INVOLUCRUM. A collection of 

 bracts at the union of several flower 

 stems. A covering of the fructifica- 

 tion of ferns and equisetums. In 

 anatomy, a name for the membrane 

 covering the heart (pericardium) 



IODINE (from iuStj, violet). An 

 elementary body, of a black colour, 

 found in lustrous scales, converted 

 by a heat of 345° F. into a beautiful 

 violet vapour. It closely resembles 

 chlorine in its chemical characters ; 

 is not found in inland plants, but only 

 in sea-weeds, and such as grow in 

 salt marshes. Its equivaleiit is 126, 

 symbol I. It combines directly with 

 metals, forming iodides. With hydro- 

 gen, it forms hydriodic acid ; with ox- 

 ygen, it forms iodic acid. Iodine, as 

 well as most of its compounds, is 

 poisonous. 



4:24 



lOLITE. A dark-blue mineral, 

 massive, and crystallized in six or 

 twelve sided prisms ; found imbed- 

 ded in primary rocks. Composition: 

 I silica, 49 17; alumina, 33 10; mag- 

 nesia, 11-48; oxide of iron, 4 33. — 

 {Slromeyer.) 



IPECACUANHA. Ccphaelis ipe- 

 cacuanha. A shrubby plant, of the 

 natural tamily CiTichoniacea, the root 

 of which is extensively used as an 

 emetic. It is a native of tropical 

 America, and especially Brazil, from 

 whence it is exported. In 20 grain 

 doses it is emetic ; but in smaller 

 quantities, expectorant. 



IPOM^EA. A genus of plants re- 

 sembling the convolvulus. 



IRIDESCENT. Exhibiting bright 

 colours by reflection. 



IRIS. In anatomy, the coloured 

 membrane of the eye which sur- 

 rounds the pupil, and, by its contrac- 

 tion or dilation, regulates the amount 

 of light entering. 



IRIS. A genus of ornamental 

 flowers, the flag. The /. Jlorenlina 

 yields the orris root, esteemed for 

 tooth-powder, from its odour resem- 

 bling violets. 



IRISATED. Exhibiting the pris- 

 matic or rainbow colours. 



IRON. A ductile metal, sp. gr. 

 7 78 ; susceptible of magnetism, and 

 taking a high polish. By exposure 

 to damp air, it absorbs oxygen, be- 

 coming rust. Its ores are very nu- 

 merous. Few soils are destitute of 

 some admixture. The ashes of plants 

 are also furnished with a small quan- 

 tity. 



Cast iron contains carbon, sand, 

 and other impurities, which are re- 

 moved, to a great extent, in wrought 

 iron. The former is brittle, harder, 

 and lasts longer when exposed than 

 wrought iron, which is ductile, soft, 

 malleable, and fibrous. 



Steel is a compound of carbon and 

 iron, remarkable for its elasticity and 

 hardness. Iron combines, also, with 

 sulphur and halogen bodies. 



The equivalent of iron is 27- 18, 

 symbol Fe (ferrum). It combines 

 with two proportions of oxygen, and 

 forms, 1st. A protoxide, 1 Fe-j- 1 0= 



