GLOSSARY. 
71 
which enters largely into the composition of several varieties of 
the trap rocks. 
Hyd rophytes. Plants which grow in water. Etym., v^wp, hydor, 
water, and (pvroy, phyton, plant. 
Hypogene Rocks. For an explanation of this term, see vol. hi. 
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 
aavpa, 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 Animalcules. 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. 
Invertebrate!) 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 htoq, isos, equal, and depfxrj, 
therme, heat. 
Jura 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. 
Kimbieridge 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 
