of Not thumber land and Durham. 85 



formed a concavity in the sides of the other. We must either 

 admit, with the late Mr. Gregory Watt, that a crystalline ar- 

 rangement of the particles can take place in solid bodies at the 

 common temperature of the earth, or that these rocks have been 

 softened by heat, or some other cause, subsequently to their for- 

 mation. Nor will even the latter opinion, I conceive, be very im- 

 probable ; for on the elevated ground at a little distance to the 

 north-west of Building Hill, I observed immense blocks of 

 extremely hard and very black basalt lying on the surface of a 

 ploughed field. On inquiry, the men who were working in- 

 formed me that numerous blocks of the same kind were buried 

 under the soil, which impeded their operations in ploughing so 

 much, that, when tliey were too large to be removed, they Avere 

 obliged to break them by blasting with gunpowder. 1 therefore 

 think it extremelv probable, that an immense whin dyke has in- 

 tersected this formation of limestone. The quarry at Fulwell 

 is close by the turn])ike road to Newcastle, and about two miles 

 from Sunderland. The limestone here presents little of the 

 honeycomb appearance of that at Building Hill ; but it is not 

 the less remarkable : it is covered by a stratum of calcareous 

 marie, or rather sand ; some of the beds are also divided by the 

 same pulverulent marie or calcareous sand, in which are im- 

 bedded numerous deticched spheres, spheroids, and also botry- 

 oidal and stalactitical masses of limetone: but the latter are at- 

 tached to the rock. The upper stratum of calcareous sand 

 also contains numerous l)alls and clusters of balls of a similar 

 kind, varying in size from that of a pea to ten or twelve inches 

 in diameter. That these balls are not water^worn is most evi- 

 dent : many of them have a crystalline diverging radiated structure, 

 others are curvedly lamellar. The most striking circumstance 

 attending these balls remains to be noticed : many of them ap- 

 pear to have come in contact at a certain stage of their forma- 

 tion : they present the appearance of two or more balls with a 

 segment cut from each, and closely united at the place of sec- 

 tion ; in other instances a number of balls appear to have pressed 

 laterally on each other and flattened the sides, thus forming 

 polyhedral prisms convex at their upper and lower extremities. 

 This singular conformation had not escaped the attention of 

 that sagacious young philosopher the late Mr. G. Watt. It is 

 indeed a fact analogous to what took place in the experiment 

 he made by melting seven cwt. of basalt, and suffering it to cool 

 slowly, A number of small globules formed in the mass, and en- 

 larged till they compressed each other into a prismatic shape. 

 The formation of these balls of limestone in the soft strata of 

 this rock would, I conceive, if properly attended to, throw some 

 F 3 light 



