ILL 



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I N D 



enormous, the average length from 

 the snout to the tip of the tail 

 being estimated by Dr. Mantell at 

 seventy feet, while, he considers, 

 some may have been one hundred 

 feet in length. This last calcula- 

 tion Prof. Buckland deems impro- 

 bable, but he gives a length of 

 seventy feet to the iguanodon. A 

 thigh-bone in the possession of Dr. 

 Mantell is three feet eight inches 

 long, and thirty- five inches round, 

 at its largest extremity. The length 

 of the hind foot is supposed to have 

 been six feet and a-half ; the cir- 

 cumference of the body, fourteen 

 feet and a-half. A most remark- 

 able appendage possessed by the 

 iguanodon was a horn of bone, 

 placed upon the nose, equal in size, 

 and resembling in form, the lesser 

 horn of the rhinoceros ; here was a 

 further analogy between the extinct 

 fossil iguanodon and the recent 

 iguana. The base of this nasal 

 horn was of an irregular oval form, 

 and slightly concave. It possessed 

 an osseous structure, and appears to 

 have had no internal cavity. It is 

 evident that it was not attached to 

 the skull by a bony union, as are 

 the horns of the mammalia. 



ILLJG'NTJS. A genus of trilobites thus 

 named by Dalman. One species, 

 Illaeuus perovalis, so named by Sir 

 R. Murchison, is described by him 

 as found in the Lower Silurian 

 rocks. It is of an elongated oval 

 form ; the central lobe of the body 

 slightly prolonged into the caudal 

 portion. 



I'MBRICATED. (Mricatus,'L'dt.) Laid 

 one over the other at the edges, like 

 the tiles of a house. In botany, 

 applied to leaves when so placed. 



IMPE'EMEABLE. Not admitting the 

 passage of fluids through its pores 

 or interstices, as clay or marl, 

 which are impermeable to water. 



I'NCTDENCE. (from in, upon, and cado, 

 to fall, Lat.) The direction in 

 which one body falls on or strikes 



another : the angle which the mov- 

 ing body makes with the plane of 

 the body struck is called the angle 

 of incidence. 



INCI'SOR. (from incisor es, Lat.) A 

 fore or cutting tooth. 



INCRUSTA'TION. (incrustatio, Lat. in- 

 crustation, Fr. incrostatbra, It.) 

 An adherent covering ; something 

 superinduced; a coating of siliceous 

 matter. 



INDECI'DUOTTS. (from in and deciduus, 

 Lat.) Not falling off; not shed, 

 as the leaves of trees, but evergreen. 



I'NDiANrrE. A whitish or grey 

 mineral, brought from the Carnatic, 

 found in masses, of a foliated 

 structure, and having a shining 

 lustre. 



I'NDICOLITE. (from indigo , and \i'0os, 

 Gr.) An indigo-coloured mineral 

 found in Sweden. It occurs crys- 

 tallised, and is considered a variety 

 of shorl. 



INDIGENOUS. (indigena, Lat. indi- 

 gene, Fr.) Native to a country ; 

 originally born, or produced, in a 

 particular country. The term is 

 more usually applied to plants than 

 animals ; thus plants, the natural 

 produce of any particular country, 

 are said to be indigenous to that 

 country. 



INDU'CTION. (mductio, Lat. induction, 

 Fr. induzione, It.) A consequence 

 drawn from several propositions or 

 principles first laid down ; reason- 

 ing from particulars to generals, as 

 when from several particular pro- 

 positions we infer one general. 

 The process by which a new 

 principle is collected from an 

 assemblage of facts, has been 

 termed induction. 



INDU'CTIVE REASONING. That kind 

 of philosophic reasoning which 

 ascends from particular facts to 

 general principles, and then de- 

 scends again from these general 

 principles to particular applications 

 and exemplifications. 



INDT/SIA. (indmia t Lat.) The case 



