40 RELATION OF UNSTRATIFIED 



primary, transition, secondary, and tertiary series, more 

 from a sense of the convenience of this long received 

 arrangement, than from the reahty of any strongly defined 

 boundaries by M^hich the strata, on the confines of each 

 series, are separated from one another. 



As the materials of stratified rocks are in great degree 

 derived, directly or indirectly, from those w^hich are unstra- 

 tified,* it will be prematm'e to enter upon the consideration 

 of derivative strata, until we have considered briefly the his- 

 tory of the primitive formations. We therefore commence 

 our inquiry at that most ancient period, when there is much 

 evidence to render it probable that the entire materials of 

 the globe were in a fluid state, and that the cause of this 

 fluidity was heat. The form of the earth being that of an 

 oblate spheroid, compressed at the poles, and enlarged at 

 the equator, is that which a fluid mass would assume from 

 revolution round its axis. The farther fact, that the shortest 

 diameter coincides with the existing axis of rotation, shows 

 that this axis has been the same ever since the crust of the 

 earth attained its present solid form. 



Assuming that the whole materials of the globe may have 



in Conybearc and Phillips's Geology of England and Wales. See also 

 Bakewell's Introduction to Geology, 1833; and Professor Phillips's arti- 

 cle Geology, in the Encyclopaedia Metropolitana ; also Professor Phillips's 

 Guide to Geology, 8vo. 1834; and Dc La Bcclie's Researches in Theo- 

 retical Geology, 8vo. 1834. The history of the organic remains of the 

 tertiary period has been most ably elucidated in Lyell's Principles of 

 Geology. 



* In speaking of crystalline rocks of supposed igneous origin as unstra- 

 tificd, we adopt a distribution wliicli, though not strictly accurate, has long 

 been in general use among geologists. Ejected masses of granite, basalt, 

 and lava have frequently horizontal partings, dividing them into beds of 

 various extent and tliickness, sucli as those wliich are most remarkable in 

 what the Wernerians have called the Floctz trap formation, PI. 1, section 

 Fig. 6. ; but they do not present that subdivision into successions of small 

 beds, and still smaller laminae, which usually exists in sedimentary strata 

 that have been deposited by the action of water. 



