514 Notices of Memoirs—Action of Acid on Limestone. 
noticed upon the broken bit of pottery what looks very like a worn- 
out inscription in Roman capital letters. This is best seen with a 
pocket lens. The bit of jet (2?) may be jet or coal ; Lam not com- 
petent to give an opinion. The fragments of flint are all artificial. 
Amone them is the base (showing the bulb of percussion) of a 
worked flake. These flint-flakes were used down into the iron age, 
and we have here another proof of the fact. The bone scoop sent by 
Mr. Swyth is, from the character of the texture or structure of the 
bone, altered by exposure and time, as it Is unquestionably older 
than the apple-scoops which schoolboys made in the present century, 
and which it closely resembles. I have another like it from the 
Lough Revel Crannog, Co. Antrim, with cobalt patina. This from 
Rathcoursey (Carrigagower) is ornamented, and the flint arrow-head 
found there is small, beautifully chipped, and of the scarce and 
deeply indented type. The iron nail is very curious, with a head 
like a horse nail. 
NOTLCHS Ot Saves Vi@iskes- 
British Assoctatron Reports. ‘Abstracts of Papers read before 
Section C. (Geology) Swansea. 
J.—On tHe Action or Carzponic Actp on LIMESTONE. 
By Proressor Boyp Dawxins, F.R.S. 
AVES in the limestone are to be looked upon as subterranean 
watercourses, which are produced partly by the dissolving 
action of the carbonic acid in the rain-water, and partly by the 
mechanical action of the streams flowing through them. The 
insoluble carbonate of lime in the rock is changed into the soluble 
bi-carbonate and carried away in solution. The additional atom of 
carbonic acid, however, is in a condition of unstable chemical com- 
bination, and if it be removed either by evaporation or by the action 
of the free current of air, the insoluble carbonate of lime at once is 
deposited. Hence it is that some caverns have their walls covered 
with a drapery of stalagmite and the little straw-like pendants from 
the roof formed round the edges of each drop gradually become 
developed into columns of various sizes. The stalagmitic pedestals 
also rise from the floor where a line of drops falls from the roof and 
ultimately unite with the column let down from above. On the 
surface, too, of the pools an ice-like sheet of stalagmite gradually 
shoots across from the sides, and sometimes where the water is still 
covers the whole surface. Admirable illustrations of all these 
processes are to be seen in the caves of Pembrokeshire, and especially 
in the Fairy Cave on Caldy Island. 
The rate of the accumulation of carbonate of lime depending 
primarily upon the access of water and the free access of air, both 
being variable, varies in different places. Sometimes it is very 
swift, as for example in the Ingleborough Cave, where a series of 
observations by Professor Phillips, Mr. Farrar, and myself extend- 
img over the years from 1845 to 1873 give the annual rate at 
‘2946 inch. It is obvious, therefore, that all speculations as to the 
