. An introduction to geology : intended to convey a practical knowledge of the science, and comprising the most important recent discoveries, with explanations of the facts and phenomena which serve to confirm or invalidate various geological theories. ted caps on several of thebills in the Vale of Thames, was probably part of one continuousbed, which has been excavated with a portion of the subjacent Lon-don clay ; such excavations and denudations are common phenome-na in almost every country. Balls of imperfect ironstone, called septaria, (of which Parkerscement is made,) are common in some
. An introduction to geology : intended to convey a practical knowledge of the science, and comprising the most important recent discoveries, with explanations of the facts and phenomena which serve to confirm or invalidate various geological theories. ted caps on several of thebills in the Vale of Thames, was probably part of one continuousbed, which has been excavated with a portion of the subjacent Lon-don clay ; such excavations and denudations are common phenome-na in almost every country. Balls of imperfect ironstone, called septaria, (of which Parkerscement is made,) are common in some parts of the London clay;branches and stems of trees, penetrated by the Teredo navalis, arefound in it, and a species of resin, to which the name of retinasphal-turn was given by Mr. Hatchett. Remains of turtles have been dugout of this clay at Highgate and Islington. Some bones of a croco-dile were discovered by Mr. Parkinson, who considers this as a soli-tary instance of the occurrence of the remains of these animals in theLondon clay. In 1830, the head of a crocodile was found by E. CROCODILE IN LONDON CLAY. 223 Spencer, Esq. of Highgate, in the London clay in the Isle of Shep-pey, of which the annexed cuts give a correct representation. The. first is an outline, being a side view of the upper jaw and teeth. Thesecond represents a front view of the head, with the two small cavi-
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Keywords: ., bookcentury1800, bookidintroduc, booksubjectgeology, bookyear1833
