GEOLOGICAL SOCIETY OF LONDON, 
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ing tlie surface with furrows like those of the chalk_, the 
softer parts of the stone then giving way^ first hollows are formed^ 
when the rotatory motion of the contents of the hollows, set in 
action by the influx and reflux of the waves, drills the pipe. 
Arguing from anolagy, he holds that similar causes produce the 
pipes in chalk. 
3. — ^^On some remarkable Concretions in the Tertiary Beds of 
the Isle of Man/' by Mr. H. E. Strickland, F.G.S.— The northern 
extremity of the Isle of Man consists of an arenaceous deposit 
forming a district of about 50 square miles, the mist extensive 
example of the marine nev.^er pleiocene in the British Isles. In 
places it attains a height of about 200 feet above the level of the 
sea. Organic remains are rather sparingly diffused in it, and 
Mr. Strickland enumerates 20 species, of which 5 are not existing 
inhabitants of the British seas. Near Bamsey the beds of this 
deposit occasionally exhibit a very remarkable concretionary 
structure, the sand has been cemented into masses, which are 
extremely hard, and even sonorous when struck, though the 
sand in which they are imbedded is perfectly loose. The ce- 
menting ingredient which the application of acid proves to be 
carbonate of lime, seems to have been influenced in its operations 
partly by the planes of stratification, and partly by the direc- 
tions in which the sand has been originally drifted by currents. 
In the former case the concretions are in the form of flat tabular 
masses, parallel to the stratification, often mammilated on their 
surfaces, or perforated obliquely by tubular cavities. In the 
latter case they assume a sub -cylindrical or spear-shaped form, 
and occur parallel both to the stratification and to each other. 
A pebble is frequently attached to the larger end of the concre- 
tion, which springs from it as from a root, to the length of a 
foot or more, and gradually terminates in an obtuse flattened 
point ; all these varieties are sometimes combined together into 
vast clusters of several tons weight, resembling masses of stalac- 
tite, the component portions being nearly parallel to each other. 
