DURHAM AND NORTHUMBERLAND.

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cannot be defined, it is not supposed to exceedthirty-five fathoms.

There is much difference in the qualities ofthe lime-stone in different parts of the county ofDurham, upon which geologists have expendedmuch experiment, and produced many enlight-ened chemical elucidations. It appears how-ever that, after the magnesian lime-stone, bluelime-stone occurs near Sunderland for aboutsixty-four feet; and after this alternations ofdark slate-clay and blue slate-clay for aboutforty fathoms ; then comes green or whin-stonefor a considerable depth, and ultimately thecoal formation.*

The lime-stone rocks about Sunderland areprobably more curious than any other partabout the formation, particularly at Building-Hill, where it is found imperfectly crystalline,and of a dark yellow or ochre colour, in someplaces dividing into small cells, united witheach other, from whence it has been called thehoneycomb lime-stone.

Numerous basaltic blocks are found scatteredabout in the surface and under the soil, asobserved by Mr. Bakewell, and are verysimilar in appearance to the large masses of

* See page II,