275 
1914-15.] Chalk Boulders from Aberdeen, etc. 
on pressure, part hard and splintery. The hard part contained three 
immature flint nodules, two about as large as a small bean, and one of 
flattened ovoid shape the size of a small walnut. The matrix is crowded 
with organisms, chiefly spheres and cells, but many Globigerinse, small 
Textularians, with several other forms, are present, the whole being 
estimated to form 65 per cent, of the material, shell fragments 2 per cent. : 
sponge spicules and Radiolaria occur, but are not common. The results of 
the analysis of this specimen were peculiar and were repeated several times. 
In the case of the softer chalk the heavier part of the residue con- 
sisted chiefly of the white granular material, with a few free spicules and 
fragments of Hexactinellid sponge mesh, some casts of Foraminifera in 
amorphous colloid silica, and also casts of Radiolaria. The rock is mainly 
calcareous, the total residue after the acid being comparatively small — 
only 3’63 per cent., — and of this nearly two-thirds was found to be 
soluble silica. 
In the harder part showing exactly the same constitution the residue 
was 12 ‘85 per cent., and of this more than eight-tenths was colloid silica, 
or 10‘75 per cent, of the rock. From the acid residue of the harder part 
it was clear that silica had infllled a larger proportion of the foraminiferal 
cells, and that some at least were partly chalcedony. 
In the final residue after treatment with potash little else remained 
but the chalcedonic casts of Foraminifera, fragments of spicules, and a 
general debris of chalcedonic particles with but few mineral grains. It 
will be noticed that the residues after treatment with acid and alkali 
closely approximate. 
B 7. — A smaller boulder roughly rectangular of hard, whitish chalk. 
The rough surface of this chalk is spotted with dark specks. When the 
smoothed sides of this block are examined, it will be seen that there are 
rounded or sub-angular areas, varying greatly in size, slightly lighter in 
colour than the surrounding material. They are not always well defined, 
but sometimes blend with the surrounding chalk. The dark specks do 
not occur in such areas, but a thin line of them often accentuates the 
division between the lighter and the darker shades. 
Seen in thin section the recognisable organisms are almost entirely 
spheres, with a very few cells of Globigerina, together forming 60 per 
cent, of the mass, the remainder being the fine calcareous paste. The 
lighter areas can faintly be distinguished by the greater density of the 
material, but there is practically no difference in the general character of 
the rock. The dark specks can now be seen to be sand grains of consider- 
able size, large fragments of Echinoid tests, ossicles or spines, and equally 
