110 James Geikie — On Changes of Climate. 



therefore, it would be hazardous to place in the " Middle Sand series " 

 any deposits of sand and gravel that happened to contain shells like 

 those of the "Manure Gravels." Quite recently, Professor Hull 

 recognized in the beds described by Professor Harkness the precise 

 equivalents of the Middle Sands of Lancashire/ and gave a section 

 showing the sand beds intercalated between an " upper " and 

 "lower Boulder-clay."- I think, therefore, that the "upper and 

 lower Boulder-clay " and intercalated shelly sands of Ireland are 

 almost certainly the equivalents of the Scottish Till, Boulder-earth 

 and clay, and interglacial deposits. 



The deposition of the "Boulder-clays" of Ireland was followed, 

 after an interval, by a period of submergence, during which the esker- 

 drift was accumulated. From the presence in this drift of marine 

 shells similar to those now living in British seas, it is quite plain 

 that the climate during this period was temperate. But after the 

 land had been submerged to a considerable depth ^ a great dispersion 

 of erratics took place, clearly showing that the temperate conditions 

 gave place to an Arctic climate. No shelly clays similar to those of 

 the Clyde have yet been detected in Ireland ; but the mountain 

 valleys, like those of Scotland, Wales, and England, abound with 

 traces of local glaciers. 



I need not refer more fully to the details of the Irish Drift. The 

 researches of my colleagues on the Geological Survey, and of many 

 other observers, clearly show that the general succession of the 

 glacial deposits in Ireland exactly coincides with that which obtains 

 in Scotland. 



For purposes of comparison I tabulate the Irish deposits, begianing 

 as before with the lower beds. 



Glacial Deposits of Ireland. 



1. Till; Boulder-clays with intercalated beds. 



2. ? (Not recognized.) * 



3. Esker drift. 



4. Erratics. 



5. Valley moraines. 



Thus wherever the Glacial deposits are examined, whether in 

 Europe or America, they appear to give evidence of the same 

 general sequence : 



1st. A lengthened succession of periods of alternate glacial and 



1 Geol. Mag., Vol. VIII., p. 294. 



2 But for various reasons 1 am not prepared to agree with my colleague's sugges- 

 tion that the " Limestone Gravel " of Ireland represents this Middle Sand group, or 

 was ever covered by Boulder-clay. I believe that the Middle Sand series of Ireland 

 (" Manure Gravels ") will be found, as they are traced inland, to thin out against the 

 gradually rising ground. It is so with the marine interglacial beds of the maritime dis- 

 tricts of Scotland ; and in all likelihood with those of the north-west of England 

 also. The erratics resting upon the gravel ridges exactly tally with those occupying 

 a similar position in Scotland, Northern Europe, and North America. 



3 Mr. Kinahan mentions the occurrence of marine terraces on Slieve Aughta at a 

 height of 1200 feet. The Eev. Mr. W. Close also refers to shelly sands at a similar 

 height on Three Rock Mountain. 



* Mr. Kinahan describes a "rocky moraine drift " which, in part at least, may be 

 the representative of the Scottish "moraine rubbish" mentioned in my last commu- 

 nication to the Magazine. 



