IN NORTH HERTFORDSHIRE. 
39 
These percentages are borne out by common observation. In 
walking in the streets of Ashwell one sees everywhere sandstone 
pebbles in the pavements of yards, sandstone boulders at the 
corners of houses, and only here and there a limestone, and occa¬ 
sionally a basalt or other igneous rock. The sandstones are super¬ 
ficially, as seen in worn boulders and pebbles, much alike, but 
when broken a good deal of variety is disclosed. I have selected 
37 specimens as representative of all the varieties we have of this 
class of materials. (See List II, p. 44.) It will be noticed that no 
attempt is made in most cases to express anything more than a 
doubtful opinion as to the beds from which these rocks are derived. 
In some cases specimens from the Millstone Grit series are identi¬ 
fied ; but in general, of hand specimens of such sedimentary rocks 
as we have, nothing very definite can be said. That many of our 
sandstone boulders come from the Carboniferous rocks seems prob¬ 
able, but there are also, no doubt, many from the Secondary rocks 
of the Midland Counties; it is impossible in many cases to separate 
with any certainty the one from the other. Of the numerous 
pebbles too small to note, which are found composing the pavements 
in Ashwell and the neighbourhood, nearly all are compact, fine¬ 
grained, yellowish or reddish sandstone. The limestones, being 
few, I have thrown into one complete list of 26 specimens. (See 
List III, p. 45.) They are generally from the Carboniferous Series, 
the Lias Marlstone, or the Oolite; derivations which agree with 
and support those assigned to the sandstones. Of the basalts only 
one is among the group of larger boulders (No. 103, in List I), but 
three others may be mentioned as of respectable dimensions; and 
the remaining four specimens of igneous rocks are noteworthy. 
(See List IV, p. 46.)*' No doubt these boulders have come from 
a more distant source than the sedimentary rocks which form the 
mass of the boulders at Ashwell. 
The large patch of boulder-clay which covers the top of the 
hill, upon which stand the church and the few houses and buildings 
which form the village of Bygrave, is similar in character to 
that on Clay Bush Hill. This is the larger of the two patches 
marked on Mr. Elsden’s map. The summit of the hill is of almost 
exactly the same elevation above sea-level as that of Clay Bush 
Hill, a “ bench-mark ” on the church being 314 feet above sea- 
level. A very indifferent section in a gravel pit on the north of 
Bygrave shows a clay, with gravel and sand similar to that on 
the opposite hill. 
I have not made any systematic search for boulders here. One 
large specimen is worth noting, however. It is of a yellowish, 
compact sandstone, lies near the church, by the road-side on the 
summit of the hill, and measures about 3 feet by 2 feet by 2 feet. 
Between these two hills is a valley, which at its lowest point on 
the section is 198ft. above sea-level, and therefore about 130 feet 
below the summits of the boulder-clay-capped hills on either side. 
* For further particulars of the igneous rocks from this district see Mr. 
Elsden’s paper already referred to. 
