39 
TO STRATIFIED ROCKS. 
rom a sense of the convenience of this long re- 
ceived arrangement, than from the reality of 
any strongly defined boundaries by which the 
strata, on the confines of each series, are sepa- 
rated from one another. 
As the materials of stratified rocks are in great 
c^Tee derived, directly or indirectly, from those 
lich are unstratified,* it will be pi’emature to 
enter upon the consideration of derivative strata, 
until we have considered briefly the history of 
the primitive formations. We therefore com- 
mence our inquiry at that most ancient period, 
when there is much evidence to render it 
probable that the entire materials of the globe 
u ere in a fluid state, and that the cause of this 
uidity was heat. The form of the earth being 
ut of an oblate spheroid, compressed at the 
poles, and enlarged at the equator, is that which 
^ ui mass would assume from revolution 
oun Its axis. The further fact, that the short- 
lametei coincides with the existing axis 
as unstrafific^'"^ crystalline rocks of supposed igneous origin 
accurate h \ ^ distribution which, though not strictly 
Partine-s ^ frequently horizontal 
such as those ct" various extent and thickness, 
have callerl remarkable in what the Wernerians 
they do tt ' P'- b section Fig. 6. ; but 
and still s ^ ^'■subdivision into successions of small beds, 
strata that ha "'^'ch usually exists in sedimentary 
Uut have been deposited by the action of water. 
