196 Mr. AlKiN o« the Wrekin^ and en the 



The lowest sandstone, called the little f'lnt^ is the eighty-fifth in 

 number, and is about fifteen feet thick ; the lower part of it is very- 

 coarse, and full of pebbles of quartz ; the upper is of a finer grain, 

 and sometimes is rendered very dense and hard by an intimate mixture 

 X)f iron ore ; it occurs at the depth of seven hundred and five feet. 

 Vegetable impressions are met with in most of the sandstone beds, 

 but I have not heard of their containing any shells. 



The clay porphyry occurs only once in the whole series ; it forms 

 a bed nine inches thick, at the depth of seventy -three feet from the 

 surface. The basis of this rock is a highly indurated clay of a liver- 

 brown colour, in which are imbedded grains of quartz, of hornblende 

 and of felspar. 



The indurated clay is mostly of a bluish-brown colour with a 

 tinge of olive, which by decomposition passes to bluish-grey and 

 ash-grey, and, when containing much iron, to ochre yellow and 

 red, and becomes very tough and plastic. In some beds it is com- 

 pact, dull and smooth, but somewhat meagre to the touch, and is 

 then usually distinguished by the name of clod ; in others it is 

 glossy, unctuous, and tending to a slaty texture, and is then called 

 clunch. It incloses subordinate beds of clay ironstone in the form 

 of balls more or less compressed, or in flat pieces of considerable 

 magnitude, and two or three inches thick. Besides vegetable im- 

 pressions, it contains a few shells ; small mytili in particular are 

 found in the iron ore, called crawstofie, which lies immediately above 

 the little flint. One of the most remarkable beds of this clay is called 

 the pinny ox penny -measure. It is the sixty-third in number, lying 

 the next below the big flint, and occurs at the depth of five hundred 

 and eighty feet. Its thickness in Madeley colhery is scarcely seven 

 feet, but at Ketley is full twenty-seven feet ; in the latter district it 

 contains subordinate beds of ironstone in flattened nodules, called pen- 



