Modern Concretions from the St. Lawrence. 2938 
The phenomenon seems to be analogous to that formation 
of nodules around organic nuclei within masses of soft mate- 
rial, which occurs in many geological formations. 
These little bodies are evidently clay concretions forined 
around vegetable fibres, and hardened by a small percentage 
of calcium carbonate, since when treated with hydrochloric 
acid they effervesce feebly and become disintegrated. They 
probably originate in the molecular aggregation of the cal- 
careous matter in the clay around any foreign body in- 
cluded in it. They are about half an inch in diameter, and 
the largest may have been two inches in length, with ronnded 
ends. When broken, they show a small central canal con- 
taining a little sand and strips of epidermal tissue, the re- 
mains of a root or stem. One shows three branches appa- 
rently proceeding in a verticillate manner from a central 
stem. In the centre, the light, reddish-brown colour of the 
clay has assumed a greenish hue, owing to deoxidation of 
the Peroxide of Iron by decay of the vegetable nucleus. 
REMARKS BY THE PRESIDENT ON CERTAIN ANCIENT CONCRE- 
TIONS, IN CONNECTION WITH THE ABOVE. 
On a small scale these modern concretions are similar to 
those so often found to enclose vegetable remains in the 
carboniferous system; and in the Pleistocene at Green’s 
Creek, on the Ottawa, vegetable stems are sometimes found 
enclosed in similar, but larger and harder concretions. 
Coneretions of this kind appear to throw light on those 
remarkable trunk-like cylinders which have been found in 
the Potsdam sandstone. These attracted the attention of 
Sir Wm, Logan many years ago ; but as they showed no struc- 
ture, external markings, or carbonaceous matter, they were 
not regarded by him as true fossils. More recently they 
have been studied by Dr. Selwyn in exposures on the bank 
of the Rideau canal, near Kingston, Dr, Selwyn has kindly 
sent photographs of these specimens, to be exhibited to the 
Society. Mr. A. Young, a student in applied science in 
McGill University, as also presented fine specimens to the 
