742 REPORT—1899, 
It seems also to be a rule for these bodies to occasionally exhibit concentric 
arrangement. A recent instance of this re-deposit of material is very frequent in 
weathered mortar, whether used as a cement for sandstone, limestone, or igneous 
rocks. So far, I have never failed to discover examples of this in whatever town 
or village I have searched. Both in dolomite and oolite beds, at Fulwell, Cress- 
well Crags, and Isle of Portland, tubes and channels, often concentrically arranged, 
are to be met with quite distinct from ordinary drainage channels. These are 
probably due to the same influence, a hydrostatic or mechanical one, which 
causes the segregation in the mixture of sand and lime used as mortar. The cone- 
in-cone rings seen in coal from Merthyr Tydvil may be due to the same selective 
power or growth, for, from an analysis made for me by Mr. E. T. Andrews, they 
contain lime and alumina in about equal parts. 
Both flint paramoudra and the flint circles near Cromer should, in my opinion, 
come under this division of concretionary bodies and no longer be supposed to he 
fossil sponges. 
Beekite, the geodes from Uruguay, and the variety of agate with ‘ eyes,’ afford 
innumerable examples of annular formation, differing in arrangement from the 
mortar only by the smaller size of the circles. Both chalcedony and opal must be 
recognised as possessing this power to produce circles and ‘ fortifications’ on flat 
surfaces quite irrespective of the contour lines of the cavities in which the agates 
are formed. 
Tron cylinders in the Folkestone beds of the Lower Greensand exist in large 
numbers as single tubes, clusters, and concentric tubes. As yet, I believe, no one 
has found any sign of organic remains in association with them. In all proba- 
bility they are due, like the other instances mentioned, to some special arrange- 
ment or concentration of solutions in the beds. They are met with to a smaller 
extent in the Trias, near Exeter, the Wealden of the south-east of England and 
other rock beds. They give little, perhaps no evidence of pressure, and are gene- 
rally found in horizontal positions, so cannot be supposed to be stalactitic. 
The actual cause or origin of these formations is not very clear. We may call 
it segregation, but this does not carry us far. Whilst further study may add to 
our knowledge of the influences which favour their growth, we may be just as 
ignorant as to why they grow as the crystallographers are of the similar pro- 
cesses in crystals. I surmise, however, that we shall ultimately find that some 
hydrostatic influence will explain much that is at present both mysterious and 
perplexing. 
4. On Photographs of Sandstone Pipes in the Carboniferous Limestone at 
Dwibau Point, Hast Anglesey. By Epwarp GREENLY. 
At Dwlbau Point, Red Wharf Bay, certain beds in the Carboniferous Lime- 
stone are traversed by remarkable funnel-shaped pipes filled with fine hard sand- 
stone. The sandstone filling the pipes can be seen to be continuous with that of 
overlying sandstone beds, from the lower side of which the pipes pass down into 
an underlying limestone. Most of the pipes are about six feet wide at the top, 
and have been followed to a depth of some six or seven feet. There are, however; 
smaller ones; and one much larger is seen in section to a depth of twelve or 
fifteen feet. The sandstone of the pipes is bedded, and there appears also to be a 
concentric structure. It is obvious that they are due to contemporaneous erosion, 
though of an exceptional kind. 
The photographs show pipes in various stages of denudation, some standing up 
four or five feet from the surface of the foreshore. 
5, Glaciation of Dwlbaw Point, East Anglesey. By EpwarpD GREENLY. 
The surface of the limestone at Dwlbau Point is magnificently ice-worn, the 
general direction of the strie being N.N.E.-S.S8.W., and the moutonnée surface 
facing N.N.E, On the sides, however, of the funnel-shaped pit surrounding one of 
