409 



each one pursues its allotted path and operations : and, like the 

 locusts, as mentioned by the prophet Joel (chap. ii. v. 7, 8.), so 

 aptly quoted by Sellius, " they march every one on his ways, and 

 they break not their ranks ; neither does one thrust another, they 

 walk every one in his path." This curious circumstance will appear 

 evidently on a view of Plate VIII. Fig. 9- 



As in the ordinary fossil wood we have perceived that its lapi- 

 deous impregnation may be either effected by the introduction of 

 lime, silex, or alumine, so also, in this variety of fossil wood, simi- 

 lar impregnations are met with* In PI. VIII. Fig. 8. is represented 

 a most beautiful specimen of silicized bituminous wood, in which 

 the ravages of the teredo are very manifest. In this specimen, the 

 filtrated silicious matter, having acquired a strong brown or yel- 

 lowish tinge, perhaps from the admixture of fluid bitumen, fills up 

 one of the cavities, left by the worm, with a transparent topazine 

 calcedony, giving an appearance exactly resembling that of the 

 larva of some insect. Its other cavities are filled with a substance 

 so strictly agatine, as to possess not only the colours, but even the 

 lines, which characterize that species of agate called the fortification 

 agate. Fig. 10. of the same Plate represents a piece of silicized wood, 

 which has the appearance of having suffered but little change from 

 bitumini/ .tion ; having rather the appearance of a dry withered 

 wood. In this specimen the cavities formed by the teredo are uni- 

 fotinlv filled by a white pellucid calcedony, apparently free from 

 any for- ipi intermixture. Fig. 9. of the same Plate is from a spe- 

 ciincn "liich is impregnated with carbonate of lime, which, in a 

 spathose state, has filled several of the tubes formed by the teredo, 

 and invested the internal surtace of others. Frequently particles of 

 pyrites may be seen intermingled with the calcareous spar: and 

 nrntly also wili the wood be so permeated by clay, as to allow 

 it to he termed alununous wood ; employing the term in that loose 



VOL. i. 3 G 



