TRANSACTIONS OF THE SECTIONS. 71 
bodies and the analogous phenomena of glaciers. Previous to the autumn of 1846, a 
large quantity of mud, dredged from the harbour of Valetta, was deposited on level 
ground between the harbour and cliff, and covered about two acres of ground; the 
autumnal rains, aided by the overflow of a tank on the cliff, caused the main body of 
the mud to flow from the side next the sea, where it was piled up highest, towards the 
cliff; the mud descended in streams whose inclinations were greatest at their origin, 
and their surface was marked by alternate curved bands of coarse and fine material, 
the rough bands being slightly in relief; where the descent was steepest, the curved 
__ bands were broken and irregular; as the surface of the mud dried, two sets of fissures 
were formed, one in the direction of the stream, the other following the curved bands. 
In the spring of the present year a smaller slide took place, in which the surface of 
the mud was raised into curved bands or waves 11 to 2 feet high, the ridges being 
formed of the coarser materials. It appears that in the first instance the surface-mud 
was semi-fluid, and flowed over a comparatively dry and hardened surface, but after- 
__ wards the surface-mud dried by exposure, whilst that below remained moist. 
An attempt to illustrate the Origin of “ Dirt-bands” on Glaciers. 
By A. Mitwarp. 
The surface of a glacier is composed of alternate bands of porous and compact ice, 
_ and the former becoming discoloured more readily than the latter, give rise to ‘ dirt- 
_ bands,” which follow the direction of the hyperbolic curves marked by the outcrop 
_ of the structural planes, known as the “ribbon” structure, which are elongated low 
down the glacier and compressed near its source ; they are also most apparent low down, 
where the ice has been longest exposed to the weather. The writer suggests that the 
porous bands may be formed during the winter season, when the ice is less saturated 
_ with water and forms more slowly; and that the compact bands mark the quantity of 
ice added to the glacier each summer, when its motion is greatest. He also recom- 
_ mends the examination of the upper part of glaciers, with the view of ascertaining 
_ whether their surface is originally marked by waves such as those before described on 
_ the mud-slides. 
On some Bones found in the Bed of the Tawey. By W. Morcan. 
On the Subsidences which have taken place in the Mineral Basin of South 
' Wales, between the Llynvi Valley on the East, and Penllergare on the 
West. By F. Mosss. 
Mr. J. G. Jeffreys exhibited specimens of the following rare and recent British 
_ shells, and species which he considered identical with them in the Crag formation. 
RECENT. FOSSIL. 
Buccinum ovum, Zwuré. B Dalei, Sow. 
Fusus scalariformis, Gould. Id., Sow. 
Saxicava arctica, var.?, Forbes § Hanley. Sphenia cylindrica, Sow. 
' Natica helicoides, Johnst. Id., Sow. é 
sordida, Lam. N, cirriformis, Wood. 
The Marquis of Northampton read a letter from M. Boguslawski on the fall of a 
_ Meteorite, in two pieces, at Braunau in Bohemia, on the 14th of July 1847. Another 
_ meteorite of larger size, but exactly agreeing in appearance and chemical composition, 
__ had been dug up from a depth of fourteen feet at See Leesgen. 
3 On the Geology of the County of Wicklow. By Prof. Otpxam, M.R.LA. 
J 
¥ This communication was illustrated by a new Geological Map of Wicklow and a 
number of sections in the mining districts, published in connection with the Geolo- 
_ gical Survey of Great Britain. Through the centre of the county passes the granite 
ridge, which extends from Dublin to Waterford, nearly N. and S.; its highest point, 
