GLOSSARY. 71 



which enters largely into the composition of several varieties of 



the trap rocks. 

 HYDROPHYTES. Plants which grow in water. Etym., i^wp, hydor, 



water, and 0i/rov, phyton, plant. 

 HYPOGENE ROCKS. For an explanation of this term, see vol. iii. 



p. 374. 



ICEBERG. The great masses of ice, often the size of hills, which float 

 in the polar and northern seas. Etym., ice, and berg, German 

 for hill. 



ICHTHYOSAURUS, a gigantic fossil marine reptile, intermediate be- 

 tween a crocodile and a fish. Etym., IX$VG, ichthus, a fish, and 

 o-avpa, saura, a lizard. 



INDUCTION, a consequence, conclusion or inference, drawn from 

 propositions or principles first laid down, or from the observ- 

 ation and examination of phenomena. 



INFUSORY ANIM ALC ULES. Minute living creatures generated in many 

 infusions ; and the term infusoria has been given to all such 

 animalcules whether found in infusions or in stagnant water, 

 vinegar, &c. 



INSPISSATED, Thickened. Etym., spissus, thick. 



INVERTEBRATED ANIMALS. Animals which are not furnished with 

 a back-bone. For a further explanation, see " Vertebrated 

 Animals." 



ISOTHERMAL. Such zones or divisions of the land, ocean, or atmo- 

 sphere, which have an equal degree of mean annual warmth, 

 are said to be isothermal, from to-oe, isos, equal, and %>/**/, 

 therme, heat. 



JU'RA LIMESTONE. The limestones belonging to the oolite group, 

 see Table II. H, p. 391, constitute the chief part of the mountains 

 of the Jura, between France and Switzerland, and hence the 

 geologists of the Continent have given the name to the group. 



KIMMERIDGE CLAY, a thick bed of clay, constituting a member of 

 the Oolite Group. See Table II. H, p. 391. so called because it 

 is found well developed at Kimmeridge in the isle of Purbeck, 

 Dorsetshire. 



LACUSTRINE, belonging to a lake. Etym., Lacus, a lake. 

 LAMINA. Latin for plates ; used in geology, for the smaller layers 



.of which a stratum is frequently composed. 

 LAMANTINE. A living species of the herbivorous cetacea or whale 



