265 
1914-15.] Chalk Boulders from Aberdeen, etc. 
what is and what is not to be included as soluble silica is perhaps a 
debatable one from the point of view of the chemist, and possibly some of 
the terrigenous matter may have been acted upon in the above process. 
A friend of acknowledged ability in the analysis of rocks has, however, 
been good enough to check my work in the case of one specimen ; the 
result found us in complete agreement. 
The Boulders from Aberdeen and the Kinnaird Deep. 
The following is a list of specimens examined, with details of their 
salient characters. To ensure identification they are numbered as 
follows: — lA to 9 A are those sent me by Dr Gibb; 1 B to 13 B, 
those I collected myself at Belhelvie ; and 1 C to 6 C are those dredged 
by the Goldseeker from the Kinnaird Deep off the north coast of Aberdeen, 
and 1 G to 22 G those found north of Scotland and in the Faroe Channel. 
In the table some of these numbers are placed in the first column, 
the specimens being arranged, with one or two exceptions, according to 
the amount of residue contained in each after treatment with acid. 
Following the figures identifying the specimen is a brief description of 
the macroscopic appearance of the rock. Then follows the percentage 
dissolved in a 20 per cent, solution of hydrochloric acid, which may 
fairly be taken to represent the carbonate of lime, plus a little carbonate 
1 
Insoluble in Acid. 
Rock. 
3 
"o 
<1 
•S 
d 
0) 
Composition of Coarse Residue. 
o 
3 
3 
w. 
Per cent 
3 
m 
3 
‘o 
3 
o 
' m 
O) 
c 
31 
C/2 
O 
O 
Minerals. 
Max. Size 
1 of Grains. 
Average Size 
of Grains. 
Organisms and 
Other Ingredients. 
A9 
A small rounded 
fragment of 
green-grey fri- 
able rock. 
None 
100 
None 
40-00 
60-00 
Quartz, mica, 
chlorite, zircon. 
-13 
•06 
A few residuary casts 
of spicular canals. 
Casts of Radio- 
laria, aggregations 
of fine siliceous 
matter. 
B 1 
A subangular 
boulder of some 
size. Colour 
when broken 
darkish grey, 
semi-crystalline. 
77-06 
22-94 
21-22 
1-72 
Quartz, mica, fel- 
spars, tourma- 
line, garnet. 
(Marcasite and 
iron pyrites. ) 
•16 
•07 
Sponge spicules, 
rod-like lengths, 
simple Monaxons, 
and many globate 
forms. Two casts 
of Ammodiscus in 
pyrites. 
B2 
An angular frag- 
ment of firm 
white chalk. 
55-11 
44-89 
19-31 
25-56 
Quartz, mica. (A 
few glauconitic 
grains. ) 
•21 
(Sponge spiculesand 
Radiolaria very 
abundant.) 
