1855.] HAMILTON TERTIARIES OF HESSE CASSEL. 133 



15. Grey saponaceous clay. 



16. Brown-coal beds (thin). 



17. Grey clay. 



18. Muschelkalk. 



The peculiar feature of this section is the occurrence of two thin 

 beds containing freshwater shells above the second coal-bed. They 

 are chiefly found in a fine, unctuous, nearly white clay, above the 

 fire-clay, and consist principally of one, if not more species of Palu- 

 dina or Bithynia, a small Planorbis, and one or two species of small 

 bivalves belonging to the genus Cyclas or Cyrena. At least these 

 were all which the rainy and muddy state of the weather allowed us 

 to obtain. 



The whole Brown-coal formation of the Hirschberg, with its asso- 

 ciated clays, and probably that of the Meissner, thus appears to have 

 been a freshwater basin or lagoon, surrounded by Bunter Sandstein, 

 with a ridge or reef of Muschelkalk passing through the centre. 



Here also I was struck, as on the Habichts Wald, with the ap- 

 parently anomalous fact of the coal-measures dipping towards and 

 under the basaltic nucleus of the hill, although in both cases the 

 basalt must be of a subsequent date, and in its elevation or protrusion 

 might have been expected to give the coal-beds a contrary or qua- 

 quaversal inclination. From the numerous cases in which the same 

 phaenomenon occurs, I was anxious to ascertain a probable cause of 

 this appearance : several explanations suggested themselves to me, 

 but they would not stand the test of inquiry, until a hint from our 

 former President, Mr. William Hopkins, our best authority in dyna- 

 mical geology, suggested an explanation, which, if not the sole cause, 

 must be admitted as one of the most likely partial causes of this 

 appearance. 



The Brown-coal beds of the north of Germany have evidently been 

 subjected to a very considerable amount of alternate elevation and 

 depression accompanied by lateral pressure. The consequence of this 

 has been, where they have not been completely broken off, to cause 

 a great amount of undulation in the beds themselves. Where this 

 took place, the natural result would be to cause fissures or openings 

 through the bed either from above or from below, accordingly as the 

 bed has been raised upwards into a saddle, or depressed downwards 

 into a trough. See fig. 2, p. 134. 



In the accompanying diagram, fig. 2, if the undulation of the beds 

 be caused by lateral pressure, a fissure would naturally take place at 

 b, in the lower part of the strata, and at a in the upper part. When 

 at a subsequent period the basaltic outburst took place, the fissure b 

 at once afforded an easy outlet for the liquid matter which then 

 filled up the hollow c d. This may have taken place when the 

 whole region was under water. When the action of tidal waves 

 or other atmospheric causes afterwards denuded the surrounding 

 country, the basaltic capping protected the underlying beds, and, as 

 the other portions have gradually wasted away as far as the line c e, 

 there would remain only the hill with its basaltic capping, c d^ and 

 the Brovi^n-coal beds cropping out at /on the slope c e, and dipping 



VOL. XI. PART I. L 



