320 HARMER : THE PLEISTOCENE DEPOSITS OF EAST AXGLIA, 
it was of diabase, suggesting that it may possibly have conir 
from the Whin Sill, which, a priori, seems not improbable. 
Igneous erratics are, however, comparatively rare in the Chalky 
Boulder-clay of Norfolk and Suffolk (Upper Glacial of Wood). 
Moreover, shells and broken shell fragments of recent species, 
such as Tellina balthica, are commonly found in the Lower 
Glacial deposits of the coast. With the exception of two cases 
given by Mr. H. B. Woodward, for which he suggests a derivative 
origin from the Crag,* such debris is, as far as I am aware, 
unknown from the Upper Glacial clay. 
It seems improbable to me that the Scandinavian glacier 
ever touched the Norfolk coast, but its southern termination 
may have lain at one time at no great distance from it. The 
Chalk debris of the Lower Glacial clays, some of it from the 
higher zones of that formation, may have been derived from 
a local source at no great distance, but the hard Chalk and grej^ 
flint came probably from the Wolds, as Mr. Reid also states. 
In appearance the Lower Glacial clays remind one of those of 
Yorkshire. The Till at Hasboro' is not unlil^e the chalky 
basement clay of Holderness, while the Norwich brickearth 
resembles the Hessle Clay ; the latter is believed to be newer^ 
however, than these Norfolk drifts. A microscopical comparison 
of the constituent materials of these deposits would no doubt 
yield interesting results, and show whether the resemblance is 
apparent or real. 
It is worthj^ of notice, as Mr. Jukes-Browne has remarked, 
that most of the clays which cover Holderness and the Lincoln- 
shire marsh-land, and spread on to the Chalk Wolds and over 
North-east Norfolk, are brown, reddish, or purple, and but 
seldom contain chalk ; they do not behave as the Chalky Boulder- 
clay does, in taking its colour and composition from the forma- 
tions traversed by the ice to which it was due. 
Whether or not the Scandinavian ice-stream reached Norfolk 
at any time, foreign geologists do not doubt that it extended as 
far as Holland and the north of Germany. Dr. Lorie, of Utrecht, 
traces what he considers to have been its greatest extension by 
♦Mem. Geol. Surv., Norwich, p. 115, 1881. 
