Correspondence—J, W. Gregory. 139 
Lough Derg and South Kildare. I inserted only thirteen out of the 
thirty-eight lines marked by Mr. Wright, as they were sufficient 
to show the general view as to the ice-movement in Mid-West 
Treland. Eleven out of the thirteen lines follow the originals 
precisely ; the two easternmost are rather generalized to show the 
movement east of Lough Ree and trend rather farther to the west 
than the nearest corresponding of Mr. Wright’s lines; but this 
difference does not affect the argument, as their direction in the 
original is athwart the chief eskers, and is inconsistent with the 
formation of the eskers by intra-glacial rivers. 
Origin of Boulder Clay.—Passing to the general question of the 
origin of boulder clay, Professor Kendall states that I intend “a 
general assertion of the marine origin of all boulder clay”’. No 
such assertion is intended. I briefly stated my view of its origin in 
Geology of To-day (p. 227). So far from claiming all boulder 
clay as marine, I described its formation in an ice-blocked depression | 
at the head of the Fulmar Valley in Spitsbergen. It is, however, 
sometimes subaqueous, deposited either in lakes or in quiet arms of 
the sea as off the Sefstrom Glacier. Each case must be determined 
by the local evidence, and where the boulder clay contains 
contemporaryforaminifera, the possibility of its origin as marine mud 
must be considered. The foraminifera cannot be simply dismissed 
as derived from older rocks when they have been determined by 
Mr. Joseph Wright. I once sent him some Essex boulder clay, and 
he reported a number of species as derived from the Chalk and a 
list of others as indigenous to the clay. Mr. J. Wright is not likely 
to make the mistake suggested. 
That the belief in the marine origin of boulder clay has been 
and is rejected by the majority of British glacial geologists is fully 
admitted in my paper. Professor Kendall asks to whom I referred 
as upholders of the marine origin of boulder clay. Professor Bonney’s 
Presidential Address to the British Association in 1910 shows 
that the marine theory has been consistently supported by high 
authorities. My own partial acceptance of the view has been 
by no means consistent, for I at first regarded all boulder clay 
as terrestrial, and was only gradually led to the view that 
some of it is marine. Amongst men with an intimate know- 
ledge of the boulder clay of the south-west of Scotland, and 
who regard it as a marine deposit, may be mentioned Mr. J. 
Neilson, for the Glasgow district, and Mr. John Smith, after his 
detailed study of the Ayrshire Drifts. The increasing faith in 
isostatic oscillations has also encouraged the probability of a 
glacial subsidence. In recent years there seems to have been a 
decided trend toward the opinions that the boulder clay has not 
yet been satisfactorily explained, and that some of it is marine. 
The consequences of that conclusion are not so startling as 
Professor Kendall suggests, for until the shell beds at 1,300 feet on 
Three Rock Mountain, near Dublin; at Moel Tryfaen, Oswestry, 
