THEIR ECONOMIC PRODUCTS. 199 



tiary and existing forms, and note in these not only the 

 further introduction of the true timber trees and the higher 

 birds and mammals, but also the still greater degree of 

 specialisation both in form and function which characterises 

 the whole ; and unless blinded by prejudice or incapable of 

 discernment, they cannot refuse assent that there has been 

 a progress, and that this progress has taken place in a way 

 so connected and definite as to lead to the unavoidable 

 conviction of an all-pervading law of development. 



As Economic Repositories the secondary formations are 

 year after year assuming greater importance. Not many 

 years ago, building-stone, limestone, lithographic slabs, 

 fuller's earth, rock-salt, gypsum, and chalk, were the prin- 

 cipal products extracted; but now ironstone like that of 

 Cleveland in Yorkshire, coal from many fields (Austria, 

 India, Indian islands, Brazil, Virginia, Vancouver, and 

 other regions), coprolites or phosphatic nodules for manure, 

 hydraulic cements, and other substances are largely obtained, 

 and as foreign surveys are extended, will in all likelihood 

 be met with in still greater abundance. The geological 

 mapping of the world, by competent authorities, is merely 

 in its infancy; * but as this proceeds the secondary systems 

 are gradully revealing a larger amount of economic treasures, 



* The survey of our own islands, though commenced many years ago, 

 is not half completed ; and those of our colonial possessions Canada, 

 the West Indies, India, Australia, and New Zealand are merely in 

 their first stages. The same may be said of other European countries, 

 most of which have made some progress with their surveys, but still 

 feel the want of more minute and accurate information. The Ameri- 

 can States survey, begun with great ardour, has been finished only in 

 a few instances ; while with the geology of South America, Arctic Ame- 

 rica, Asia, and Africa, we have the slightest and most imperfect ac- 

 quaintance. Till all these areas have been more thoroughly explored, 

 it were presumptuous to dogmatise, and idle to speculate, either as to 

 the scientific aspects or the economic importance of the several stratified 

 systems. 



