II 



KODENTIA. 



BODENTIA. 



Thai granular or atccharoid limestone is found by the tide of the 

 latltic dyk-s in Antrim, on the greenstone of Teesdale, near the 

 byp*rtheue of Sky, Ac. The limestone among primary strata ii of 

 aimilar appearance, though not in contact with igneous rook*. 



4. Carbonaceous Rocks. Coal becomes ooke or anthracite near 

 basaltic dykes. 



Examination* of this kind bare shown that ordinary sedimentary 

 rocks altered by heat acquire aipecU and structures and compositions 

 resembling almost exactly those most common among the earliest or 

 primary strata, as quartz rock, elay-slate, garnet mica-slate, garnet 

 gneiss, granular marble, Ac. ; and it is therefore a probable inference 

 that in all such cases of strict resemblance those ancient rocks have 

 undergone on a great scale, and under the general influence of the 

 intense heat of the earth, the changes which are certainly proved to 

 hare happened locally, from limited agencies, on substances of similar 

 chemical quality. Very careful investigations on these points are 

 however still needed to fix limits and give precision and certainty to 

 the inferences from phenomena. [BASALT; GRANITE; GRAUWACKE; 

 QxEias; LAVA; MICA-SCUIST; Pom-urnr; STRATIFICATION.] 



RODE'NTIA, an order of Animals belonging to the class Mammalia, 

 embracing the Rats and Mice, Hares. Rabbits, Guinea-Pigs, and other 

 well-known animals. 



The following is Mr. Watcrhouse's arrangement of these animals : 



front only, so that their posterior border being worn away more than 

 their anterior edge, they are always kept set like a chisel ; their pris- 

 matic form causes them to grow from the root in proportion to the 

 wearing down of their cutting edge ; and this disposition to grow or 

 push forward from the root is so strong, that if one of them is lost or 

 broken, its antagonist, meeting with no opposition to keep it within 

 bounds, develops itself so as to become monstrous. [HEAVER,] The 

 lower jaw is articulated by a longitudinal condyle, so as to have no 

 horizontal movement except from behind forwards, and vice verso, 

 convenient for the action of gnawing ; the molars consequently have 

 flat crowns, the enamelled eminences of which are always transversal, 

 so as to be in opposition to the horizontal movements of the jaw, and 

 to be better adapted for triturition. 



Tbe genera in which these eminences are simple lines, and which 

 have the crown of the tooth very flat, arc more exclusively frugivorous ; 

 those which have the eminences divided into blunt tubercles are omni- 

 vorous ; and, finally, the small number of those which have points 

 more willingly attack other animals, and approximate a little to the 

 Carnifora. 



The form of the body of the Rodents is in general such that their 

 hinder parts exceed their anterior ones, so that they leap rather than 

 walk ; this disposition in some of them U as excessive as in the 

 Kangaroos. 



Ths* animal, have two great Incisor teeth in each jaw, separated 

 from the molars by a wide space, with which they could hardly seize 

 a living prey, or rend flesh ; they could not even cut aliments, but 

 they might serve for reducing them by continued labour into fine 

 molecule* in a word, for gnawing them ; whence the term Rodents, 

 or Unmwers, applied to this order. With these weapons they attack 

 the hardest vegetable production*, and frequently feed on wood and ' 

 bark. The better to effect this object, these iucuors have enamel in 



The intestines of the animals of this order are very long; their 

 stomach simple or slightly divided; and their csccuui often very 

 voluminous, even more so than the stomach. The Myoxi (Doriuicu) 

 want the occmn. 



The brain of the Rodents is nearly smooth and without convolutions; 

 the orbits are not separated from the temporal fosstc, which have but 

 little depth ; the eyes are entirely directed laterally ; the zygomatic 

 arches, delicate and curved below, announce the weakness of the jaws ; 



