1814.] Northumherlafid, Durham, &c. 415 



along the coast some miles beyond Sunderland Bridge. I do not 

 know whether it goes so far south as the Tees, but am inclined to 

 suspect that it does It may be even connected with the magnesian 

 lime-stone of Yorkshire and Derbyshire, analysed many years ago 

 by Mr. Tennant; but the determination of this point must be left 

 to future observers. It seems to be broadest upon the banks of the 

 Wear ; but I do not conceive its greatest breadth to exceed four or 

 five miles. 



I do not know its thickness ; I have seen quarries which appeared 

 to my eye nearly 100 feet deep. The surface is uneven, rising into 

 round backed hills, or rather knolls, for they scarcely exceed 20 or 

 30 feet in height. The thickness cannot any where be very consi- 

 derable, as coals have been wrought under the magnesian lime-stone 

 west from Sunderland. No pit indeed, as far as I know, has been 

 sunk directly through the lime-stone to the coal beds; but coal 

 beds have been followed and wrought after they have passed under 

 this lime-stone. 



To form some notion of the position of this rock, I examined 

 four different hills, which had been long wrought to a great extent, 

 and were therefore well exposed. Three of these hills were com- 

 posed of distinct beds, dipping very gently to the south-east ; but I 

 could not perceive any appearance of stratification in the fourth hill. 

 Whether this was owing to the action of the weather, for it alone of 

 all the four was not wrought as a mine, or that no strata in fact 

 existed, I cannot say ; but I observed two other differences between 

 them no less striking. The stratified hills had a crystalline texture, 

 a glimmering lustre, and abounded in crystals, which on the spot I 

 considered as swine-stone, and which, when rubbed, gave out a 

 strong bituminous odour; but I cannot find that this is the case with 

 any of the specimens which I brought with me. Hence I am 

 unable to determine whether 1 was mistaken in my observations or 

 not ; and I wish that some gentleman on the spot would examine 

 the matter anew. Building Hill is the place where these crystals 

 most abound. I analysed some of them, and found them destitute of 

 magnesia, or at least very nearly so. The hill, in which no stratifica- 

 tion could be perceived, was composed of a porous soft stone, and 

 was full of the casts of shells, corals, and other marine productions. 



There is a very extensive quarry, called Fullwell, about a mile 

 north of the Wear, at Sunderland Bridge. Above the rock there 

 are a few feet of earth (probably decayed lime-stone), which is full 

 of round lime-stone balls, of various sizes. They were sometimes 

 quite spherical, and sometimes botryoidal. In the centre of each 

 ball there occurs a small cavity, the walls of which are lined with 

 minute crystals. Th< internal colour in some balls is light ochre- 

 yellow, in others yellowish-grey; lustre, glimmering; fracture, 

 even, splintery, 'i here ;irc evident traces of a tendency to crystal- 

 lization, especially towards the surface of the ball, and then the 

 Imtre is more considerable; very solid, and difficultly frangible; 

 bwdaetsj that of luaeatoo* ; specific gravity, 2*649. These balls, 



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