6 The Irish Naiuralisf. January, 
It had been hoped that the source of origin of the three 
Boulder-clays which were examined would be shown by a 
careful review of the evidence obtained from the Mollusca 
and the erratics. That the brownish Boulder-clay came from 
the southward may be assumed at once, all the available 
evidence supporting that view. The points of origin of the 
Glenulra Till and the Belderrig Telhna-clay is much more 
obscure. It is clear that both came from the northward, 
the abundance of shells and shell -fragments proving this 
beyond question, but we are unable to make any definite 
statement beyond that. A considerable coUection of 
erratics was made from each horizon visited, and efforts 
were made to find some t^^pical rocks which could be traced 
to Donegal. This ended in failure, because sandstones, 
grits, limestones, mica-schists occur also in the Sligo district, 
and such granites as were found may also have come from 
the direction of the Ox Mountains. Mr. Kilroe, of H.M. 
Geological Survey, Vv^ho very kindly looked over the col- 
lection, could find nothing typical of Donegal, and con- 
sidered that the facies of the collection pointed to the Sligo 
and east Mayo direction. The matter must remain in 
this state for the present, but the possibihty that the 
Belderrig TelHna-clay was brought by floating ice must not 
be overlooked. This deposit is so limited in extent, and 
occurs so near the present coast -line that even one large 
berg could have swept the Telhna-clay into its present 
position. 
I have to thank Mr. R. J. Ussher, of Cappagh, for much 
friendly advice regarding this rather out-of-the-way district. 
National Library of Ireland. 
