58 Rev. J. G. Cumming on some of the more recent 



directed attention to certain accumulations in the Isle of 

 Man of boulder clay with post-pleiocene sands, capped by ex- 

 tensive terraces of drift gravel, and from an examination of 

 the contents of these beds I endeavoured to trace out the gene- 

 ral direction of the currents in the neighbouring seas at the 

 period of their deposition. In the present paper I wish to point 

 to a few facts bearing upon the subsequent removal of a large 

 portion of them, and the formation of the basin now occupied 

 by the Irish Sea. 



I look upon the Isle of Man as affording, from its central 

 position, an admirable clue to the changes which have taken 

 place in this area, and as presenting to us a gauge by which 

 to measure the relative level of the sea and land in the middle 

 portion of the British Isles. For there is no evidence of any 

 elevation or depression in more recent geological times affect- 

 ing the Isle of Man per se, and not extending in a greater or 

 less degree to the surrounding countries. All the evidences 

 of later movements appear to be common to it and the sur- 

 rounding coasts of Great Britain and Ireland. 



I do not now enter into the question as to how the changes 

 in the relative levels of sea and land were brought about, whe- 

 ther by the alternate elevation and depression of continents 

 affecting the general level of the ocean, the change in intensity 

 of gravitation at particular localities, or the absolute depres- 

 sion and elevation by volcanic or other agency of this portion 

 of the globe. I have now simply to trace out certain facts 

 indicative of considerable movements of an oscillatory charac- 

 ter affecting the relative level of the sea and land, and to en- 

 deavour to point out those of the most recent date which have 

 given their present contour to the shores surrounding the Irish 

 Sea. 



In various memoirs which I have read before the Geologi- 

 cal Society of London during the last ten years, I have de- 

 tailed the facts which lead me to the conclusion that during 

 the deposit of the boulder-clay {which was a period of depres- 

 sion, and in which the climate of this region was of a more 

 arctic character than is at this present time experienced), 

 there was a gradual submergence of the Isle of Man, and (as 

 I believe), of the coasts of the countries immediately around it 



