KIRKCY — SANDPIPES IN MAGNESIAN LIMESTONE 0¥ DURHAM. 295 
new tliooiy of the origin of sand-pipes, but because it is well that tho 
oecnirreiicc of such as are found in other calcareous rocks than chalk 
siiould be recorded, and especially when in rocks which differ from 
the latter in general structure and greater hardness. 
The tubular cavities or pipes, that I am about to notice occur in a 
new (juarry belonging to Sir Hedworth Williamson, which has been 
lately opened on tlie northern slope of an eminence of the magnesian 
limestone called Fulwell Hill, and which is about a mile and a-half 
north of Sundei'land. The summit of the hill is about two hundred and 
thu'ty feet above the sea, but the site of the pipes is only about one 
hundi'ed and fifty feet above that level. The limestone of this hill 
belongs to the upjjer portion of the magnesian limestone series, being 
the upper limestone of Howse, and the crystalline, earthy, and com- 
pact limestone of King. This eminence, like most of the sm-round- 
ing countiy, is covered more or less with boulder-clay, the covering 
being comparatively thin on the top, but of greater and increasing 
thickness on the slopes and lower levels. 
On the northern slope of the hill, and at the site of the pipes, the 
boulder-clay has been removed, and in its place are beds of sand, and 
clay without boulders, with some shingle and gravel. The limestone 
surface is also worn here, and has every appearance of having once 
occupied a position between tide marks — at least, it has the appear- 
ance of having been subjected to the action of water. But to pro- 
perly understand the relation of these beds to the limestone surface, and 
to the pipes in the latter, I refer to the accompanying woodcut (fig. 1), 
which gives a transverse section of the deposits i am describing. 
The contoiir of the general surface is given by the line a a, and the 
worn surface of the limestone by h b, which at b' takes the form of a 
low terraced cliff", the ledges being smoothly rounded, and in some 
places rather hollowed out beneath. Against the face of this cliff" is 
piled an in'egnalar mass of gravel and shingle, the pebbles being 
chiefly from the magnesian hmestone, with others derived from the 
boulder-clay, some of the former being sub-angular. Very little 
order is to be observed in the arrangement of the gravel, it being 
heaped against the rock just as we sometimes see gravel thrown 
against the base of a cliff" on recent coasts : some of the pebbles are 
coated with calc sinter. Immediately upon the surface of the lime- 
stone, and occasionally in sHght hollows of it, are large boulders, c c, 
of mountain limestone, basalt, and other rocks, which are most 
undoubtedly the heavier boulders of the boulder-clay originally cover- 
ing this surface, the greater weight of which has enabled them to 
withstand the denudative forces which removed the rest of that 
deposit from this area*. Upon the surface of the limestone, and 
* This is the case where the drift, or boulder clay, is now being denuded on 
the Durham coast. I know of several instances of the kind in the neighbour- 
hood of Sunderland, one of the best occurring about two miles or more to tho 
north of the harbour, on a level tongue of limestone called Wliitbum Steel. 
Scattered over its surface are some dozens of large boulders of mountain-lime- 
stone, magnesian-Umestone, millstone-grit, and basalt, the majority being par- 
