LAMPLUGII : LARG?:il BOULDERS OF FLAMBOROUGII HEAD. 399 
In this, as in my previous Flamborough lists, the chief feature 
is the great scarcity of Secondary boulders of the requisite size, and 
the high proportion of blocks demonstrably from the Carboniferous 
system. It is necessary to point out, however, that though as a rule 
the drift here contains no chalk, yet in the morainic gravel already 
mentioned, and also in the lowest bed of boulder clay in one or two 
places, there are numerous partially-rounded blocks of hard chalk, 
evidently derived from the immediate neighbourhood, which, though 
they are truly boulders, cannot be distinguished on the shore from 
blocks derived directly from the solid chalk, and are therefore 
passed without record. 
In reckoning the proportion of Carboniferous rocks, it must be 
remembered that, besides the Limestones and Sandstones, the greater 
portion of the Basalts also, which are usually the most numerous of 
all the boulders, have probably had their source in the sills and 
dykes of that system. Mr. Barker's microscopic examination has 
demonstrated that the Whin Sill " in particular has been freely 
laid under contribution. With the Basalts added, the proportion of 
Carboniferous rocks rises to between 80 and 90 per cent, of the 
whole, a result which is sufficiently remarkable when we consider 
the distance of Flamborough Head from the nearest borders of the 
system. 
The great relative abundance of the Basalts is obviously owiug 
to the superior durability of this rock, and to the character of its 
jointage which favours the production of massive loose blocks. 
In the last paper of this series I compared the Flamborough 
Head boulders with the erratics of the Holderness coast, as illustrated 
by a list of five hundred compiled on the beach near Withernsea. 
The comparison yielded many features of interest, and I have there- 
fore continued this line of investigation, and have made similar lists 
at various places both north and south of the headland. 
. These lists are condensed in the following tables. It must be 
remembered that in each case I have reckoned only those boulders 
which are over one foot in diameter. My plan of working has been 
to start fi'om a given point, and catalogue in order every erratic I 
could find which was of the requisite size, until a Hst of the desired 
length was obtained. 
