58 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



areas and added to that respecting the western. The coal-bearing 

 deposits equivalent to the Hastings sand are his Middle Wealden ; 

 his Lower Wealden is equivalent to the Purbeck beds of England, 

 now placed in the Jurassic. The whole Wealden of Struckmann is 

 only 15 meters thick under the city of Hannover; the Hastings sand 

 is thin but contains an unimportant seam of coal. At Neustadt, 10 

 miles farther northwest, the sand is still present, though very thin, 

 and holds thin coal, which has been utilized. At 24 miles west- 

 northwest, the sand is insignificant, almost wholly replaced by a 

 thick, often bituminous clay and marly shale, shale, rich in pyrite, 

 but holding some coal. 



The Hastings sand increases southwardly. At 10 miles west 

 from Hannover, thick beds of sandstone appear; on the Diester, 

 south from that city, as well as on the Siintel ridge at the southwest, 

 sandstone prevails ; but at Osterwalde, sandy and clayey shales are 

 abundant, though there are prominent beds of sandstone. Struck- 

 mann compares several sections, I., on the Diester by Credner; H., 

 farther west by himself; HI., on Osterwalde by Credner; IV., at 

 Rehburg, northwest from Hannover, by himself : 



In I., there are 12 worthless seams and three workable; in II., 3 

 worthless and one workable ; in III., 6 worthless and 5 workable ; 

 in IV., one workable.^ In HI., sandy shales or very slightly con- 

 solidated sandstones, but in IV. clays and marls make the greater 

 part. These observations by Struckmann show that the source of 

 sediment was south from Hannover and that the sand flats de- 

 creased toward the west and north, giving place to less coarse 

 materials. The coal seams are irregular and it is evident that many 

 of them are of insignificant lateral extent. Sphserosiderite is abun- 



' It would appear that in these calculations any seam yielding good coal 

 and more than ten inches thick is thick enough to be mined. 



