THE SECONDARY AGES. 



THE SECONDARY AGES, EMBRACING THE NEW RED SANDSTONE, OOLITE, 

 AND CHALK SYSTEMS THEIR PLACE IN GEOLOGICAL HISTORY 

 COMPOSITION AND SUCCESSION OF THEIR STRATA PHYSICAL CON- 

 DITIONS UNDER WHICH THEY WERE FORMED THEIR FOSSIL FLORA 

 AND FAUNA EXCESS OF CHAMBERED SHELLS EXUBERANCE OF 

 REPTILIAN LIFE CURIOUS PHASE OF BIRD-LIFE THE ARCH- 

 -EOPTERIX LIFE-CONDITIONS OF THE SECONDARY PERIODS- 

 ECONOMIC PRODUCTS OF THE SECONDARY SYSTEMS SECONDARY 

 COAL-FIELDS THEIR GROWING IMPORTANCE. 



the earlier geologists arranged the rocks of the earth's 

 crust into Primary or first-formed, Secondary or second- 

 formed, and Tertiary or third-formed, they made a most 

 important improvement in geological classification; and 

 though a somewhat different meaning is now attached to 

 these terms, they are still retained in the nomenclature of 

 the science as general and convenient designations. Accept- 

 ing PRIMARY merely in the sense of early or ancient, it em- 

 braces all the stratified systems prior to the New Red Sand- 

 stone ; while SECONDARY, on the other hand, refers to the 

 New Eed Sandstone, the Oolite and Chalk. Even this 

 New Red Sandstone, when critically examined, is found to 

 differ widely in its fossils the lower portion containing 

 palaeozoic forms closely related to those of the Coal-measures, 

 while the upper portion is characterised by mesozoic forms, 

 or such as have a closer relationship to those of the Oolite 

 and Chalk. In this way the " New Ked Sandstone " of our 



