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222 SCIENCE-GOS STP. 
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CONDUCTED BY EDWARD A. MARTIN, F.G.S. 
To GEOLOGICAL EXCHANGERS.—It is proposed 
to hold a meeting once a month, at the offices of 
SCIENCE-GossiP, 110, Strand, London, of those of 
our geological readers, who wish to exchange speci- 
mens. This will afford opportunity to arrange 
exchanges personally, without the trouble and 
expense of packing and postage. The dates of the 
meetings for the next four months will be 
December 6th, January 1oth, February 7th, and 
March 7th. The Departmental Editor for Geology 
will be present between 5 p.m. and 7 p.m., and it 
is hoped that geologists will come with their 
specimens. The geological books in the library are 
available for loan to the readers attending.—[ Editor, 
SCIENCE-GossIP. ] 
THE Surrey Bourne.— Much of the water 
supply of Croydon is drawn from springs which rise 
in the middle of the town, and this supply is assisted 
by the intermittent stream known as the Bourne. 
The rising of the Bourne was, previous to the building 
of the culvert in 1850, the cause of inundations in the 
lower parts of the town. The stream was very 
voluminous in the yeais 1841, 1852, 1866, and 1873. 
At the last-named period the rise was particularly 
high, and on the 7th February two and a half million 
gallons entered the culvert, whilst the outflow was no 
less than 9¢ million gallons. It has been estimated 
that one of these periodical risings of the Bourne 
takes place in February of the year, following that in 
which the local rainfall exceeds 30 inches. The 
Croydon water supply is augmented by a reservoir in 
the chalk at the Addington Hills, and also by the bore- 
hole recently sunk at Waddon. Another boring is 
now being made into the chalk at Woodside.—Z. 4. 
Martin. 
STRIAE AS EVIDENCE oF IcE-AcTION.—Mr. 
Martin has done well to direct attention (ante, p. 158) 
to the mischievous old theory that striae upon rocks 
are evidence of ice-action. Asa matter of fact, ihey 
are evidence of nothing at all, except the inroads of 
the weather, lichens, etc. No doubt we all remember 
attending so-called geological lectures in our young 
days, and we still carry pleasant reminiscences of the 
_.exhibition thereat of a slab of sandstone from the sea- 
shore grooved with ripple marks. These the rhetorical 
lecturer unhesitatingly referred to the action of the 
seas of some antediluyian period. The idea that this 
regular and beautiful grooving was wrought so very 
long since, is calculated to excite a poetical feeling, 
akin to that which arises when some delicate striae on 
rock surfaces are attributed to a glacial agency 
operative many centuries ago. For instance, the 
grand rocks edging the valley where the Derwent- 
water reposes have been found carved and grooved 
with striae, all pointing in the same direction. The 
bright poetical imagination of the late Mr. Ward was 
satisfied with nothing less than a monster glacier 
filling up the valley, and moving slowly northwards, 
chiselling the adjacent hills as it passed. [His 
*“ Dream on Skiddaw ~ is worthy of the poetical land 
where his geological work was so vigorously carried 
on. In all these cases, the ‘‘ glacial nightmare” is 
much enhanced in effect by the chance discovery ofan 
apparently outlying boulder, or a perched block, 
picturesquelysituated.— Dy. P. QO. Keegan, Patterdale, 
Westmoreland. 
SANDSTONE TuBes.—To my mind, the origin of 
these tubes (S.-G., ave, p. 189) usually given, will not 
explain all the conditions, so I append an abstract of 
my. paper on ‘* Tubular and Concentric Concretions,” 
read in Section C. British Association, Dover meeting, 
1899: ‘‘ After excluding stalactites and pseudomorphs 
from the list of tubular concretionary bodies, there 
yet remain a remarkable series of rings and cylinders 
which afford no obvious explanation of their exist- 
ence. They consist chiefly of lime, silica, and iron, 
and no other substances appear to possess this 
peculiar property. It seems also to be a rule for these 
bodies to occasionally exhibit concentric arrange- 
ment. 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, an hydro- 
static 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 be fossil sponges. Beekite, the 
geodes from Uruguay, and the variety of agate with 
‘eyes,’ afford innumerable examples of annular forma- 
tion, 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. Iron 
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 in any signs of organic remains in asso- 
ciation with them. In all probability they are due, 
like the other instances mentioned, to some special 
arrangement 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 Eng- 
land and other rock beds. They give little, perhaps 
no evidence of pressure, and are generally 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 segrega- 
tion, 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 processes in crystals. I surmise, however, 
that we shall ultimately find that some hydrostatic 
influence will explain much that is at present both mys- 
terious and perplexing, or that amorphous matter has 
learned the ‘trick,’ like crystals, of forming definite 
shapes. I showed a considerable number of these 
concretions from different beds, at the recent 
Soiree of the Geological Association.” —Geo. Abbotd, 
M.R.C.S., Tunbridge Wells. 
