1857.] TRIMMER — BOULDER-CLAYS. 171 



forced across this lake without filling it, and up the acclivity on which 

 they now rest. Within the mound also, or between it and the lake, 

 are many detached heaps of stones and detritus, as if left by the 

 glacier in its retreat. The singular aspect of this remarkable accu- 

 mulation of angular stones, at once arrests the attention of the spec- 

 tator, and leaves no doubt that they must have been brought together 

 by a very different agent (or, at least, acting in a very different man- 

 ner) from the one, however powerful it might be, that laid down the 

 large boulders irregularly scattered over the moor to the west. 



8. On the Upper and Lower Boulder-Clays of the Gorlston 

 Cliffs in Norfolk. By Joshua Trimmer*, Esq., F.G.S. 



During a recent visit to Norfolk, my friend, the Rev. Mr. Gunn, 

 kindly drew my attention to a fact which cleared up some anomalies 

 that had previously perplexed me while adopting the classification of 

 previous observers respecting the tertiary deposits of the district, 

 which are more ancient than the Boulder-clay. 



The new fact then brought to my notice, while it removes those 

 anomalies, confirms the views which I published in 1847 of the 

 boulder-clay being the littoral deposit of an arctic sea advancing over 

 sinking land-|\ 



It appears that in the Gorlston Cliffs there are two boulder-clays 

 separated by a mass of sand, which, on the authority of Woodward, 

 has hitherto passed for the Crag, a term which has now become as 

 indefinite as that of "drift" or "drifts." The lower boulder-clay 

 is the tailing- off of that so well known for its blocks of Scandinavian 

 origin, and which extends over the north of Europe and into the 

 eastern side of England. The upper boulder-clay is characterized by 

 an abundance of oolitic detritus. I had traced these oolitic boulders 

 over the south of Norfolk to the point at which they crossed the 

 chalk-ridge of the S waff ham Downs at Lopham Ford, and I had sup- 

 posed that the oolitic and the Scandinavian erratics met on the same 

 level; whereas Mr. Gunn's observations establish the fact that the 

 former overlaps the latter, with a mass of sand interposed. In 

 my examination of Norfolk during the three years preceding 1847, I 

 had bestowed only a slight examination on those cliffs, as being out 

 of the district on which I had undertaken to report ; and the anomalies 

 in the structures which had perplexed me were these. The base of 

 the whole series at Cromer and Gorlston is the green fluvio-marine 

 clay and the fossil forest which it supports ; and, if the sands which 

 succeed it are the Crag, we have the forest in one case above the 

 Crag and in the other below it. This anomaly will be found 

 noticed in my paper in the Journal of the Royal Agricultural So- 

 ciety, though I did not attempt to explain it. 



* Owing to the lamented decease of Mr. Trimmer since the reading of this 

 paper, it has not had the henefit of being revised by him previously to publica- 

 tion.— Ed. Q. J. G. S. 



f Journ.R. Agricult.Soc.vol. vii.part 2 ; also Quart. Journ.Geol. Soc. vol.vii. p. 19. 



