422 HARKER : PETROLOGICAL NOTES. "1 
in identifying among our boulders any of the well-known dyke- 
rocks of Durham and Northumberland, though it is quite possible ' 
that such might occur. I 
Mr. Lamplugh has forwarded me a specimen from a remarkable . 
boulder (12 inches x <S x 4) in the Lower Boulder-Clay of Upgang, ^ 
near Whitby. It has the appearance of a brecciated flint, the vein- j 
like spaces dividing it being marked either by opaque matter or by a | 
curious pink colour ; but in the yellow-grey flinty mass itself are 
seen numerous little globules recalling a spherulitic structure. A 
slice [1253] shows that the original substance, perhaps a rhyolitic j 
lava, has been replaced by more or less distinctly crystalline silica 1 
with a patchy arrangement ; while the little globular bodies show a j 
radial structure, which gives a good "black cross." The whole \ 
reminds one closely of the micro-structure of some so-called " moss- I 
agates." ' 
In the foregoing notes I have endeavoured to abstain from any 
speculations not directly prompted by the specimens. The only ' 
definite results arrived at may be briefly summarised here : (i.) i 
Among the boulders examined are some certainly from the south ' 
and west of Norway ; (ii.) most of the granitic, gneissic, and crystal- \ 
line schistose rocks are referred with probability to the same source ; J 
(iii.) other boulders have been furnished by the northern and j 
eastern parts of the English Lake District ; (iv.) others have been 1 
derived from Teesdale ; and (v.) others again have come from the j 
Cheviot Hills and the southern part of Scotland. | 
In conclusion, I should like to call attention to a feature which j 
I have noticed in one or two specimens of limestone boulders, and 
which may be found to be of more frequent occurrence. It is well - 
exhibited by a small sub-angular boulder of dark crinoidal limestone, j 
doubtless Carboniferous, from the clay nearly below Flamborough 1 
Lighthouse. The specimen is three-and-a-half inches long, and is *, 
scratched in at least three directions. Its surface shows three or 
four rather angular depressions or shallow pits, which are polished , 
like the rest of the stone, but have only a few scratches. There can | 
be little doubt that this is an example of the " impressed limestone , 
pebbles " noticed by Dr. Sorby and others ; the little pits, which are 
i 
