STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 137 



marine and largely calcareous ; but in a part of France, the closing 

 stages are characterized by thick fresh-water deposits and thin 

 seams of lignitic coal have been observ^ed. Land deposits abound 

 in eastern Germany and there coals are found, which at times attain 

 economic^^* importance. The Hastings Sand of England, at base 

 of the Wealden, is thought to be a delta deposit ; if so, the areas re- 

 ■maining may mark, in greatest part, the submerged portions, as 

 ■they contain no coal and the sand holds much driftwood. This 

 formation has been recognized in France, where within small areas, 

 •some coal seams exist which have been mined. The Wealden is 

 exposed within a large space in Hannover, reaching westward from 

 the Harz Mountains to the Holland border, where it underruns 

 newer formations. At this western limit, the deposits are fine 

 clays or marls with important limestones, but no coal. Coarse de- 

 posits are reached farther east and with them the coal. The seams 

 are usually thin and irregular, but occasionally one is more than 5 

 feet thick. In a section, toward the west, where shale, more or less 

 argillaceous, predominates, a workable seam occurs, but it is asso- 

 ciated with the principal sandstone of the section. The coals of 

 New Zealand and Queensland either rest on sandstone or are sep- 

 arated from it by thin clay or shale. 



The immense area of Cretaceous in the United States and Can- 

 ada affords ample opportunity for comparisons. Each formation, 

 with possible exception of the Niobrara, is coal-bearing. The 

 chief source of detritus was at the west, though important contribu- 

 tions were received from the southern border, which probably lay 

 in northern Mexico, not far from the international boundary. 



The Laramie marks the closing stages of the Cretaceous and, 

 where the succession is complete, deposition appears to have been 

 continuous into the Eocene. Except in a portion of Alberta, where 

 a brackish-water fauna is found, the rocks are of continental type ; 

 leaves abound in many beds and the animal remains are of river or 

 pond forms. The conditions recall those observed on the great 



i-*-* It should be noted that this term, " economic importance," has not the 

 same signification everywhere : in the United States, a coal seam, less than 

 thirty inches thick, is not thought to be workable, except in localities without 

 raihvay communication. On the continent of Europe seams very much thinner 

 have been worked. 



