426 BATHYMETRICAL SURVEY OF 
Comparing the results of the investigation of these two samples, it 
will be seen that as the depth increases both the percentage and the 
diameter of the minerals decrease, the proportion of vegetable matter 
also decreasing. 
The high percentage of lime in the second analysis is probably due 
to fragments of shells. 
(4) Y ell oiu- grey Clay. 
One sample was taken off Cherry island in 95 feet, and eight samples 
off the south-east coast, east of Inverfarigaig, in 250 feet. This is very 
clayey in character, being soft to the touch and plastic when wet, 
coherent when dried, and taking in the latter state a light brown streak 
if rubbed with a hard smooth body. 
The Cherry island sample is made up of : — 
Minerals (1 per cent.), angular, mean diameter 0*1 mm. : quartz, 
orthoclase, chlorite, and ferrugineous matter. 
Fine washings (99 per cent.), composed of clay and very fine mineral 
particles. 
Chemical Composition. 
Total silica ... ... ... ... ... ... ... 58*42 
Ferric oxide ... ... ... ... ... ... ... 9*51 
Alumina ... ... ... ... ... ... ... 24*58 
Lime 0 *52 
Magnesia ... ... ... ... ... 3*74 
Manganese ... ... ... ... ... ... ... 2*11 
Copper oxide ... ... ... ... ... ... ... 0*65 
Loss on ignition ... ... ... ... ... ... 0*59 
100*12 
One of the eight other samples is made up of : — 
Minerals (29 per cent.), angular, mean diameter 0*1 mm. : quartz 
and decomposed felspar, with a decomposed ferrugineous mineral. 
Fine washings (71 per cent.), composed of vegetable matter (4*2 per 
cent.) and clay and mineral particles (66*8 per cent.). 
Chemical Composition. 
Total silica ... ... ... ... . . .• ... ... 50 *94 
Ferric acid ... ... ... ... ... ... ... 14*76 
Alumina ... ... ... ... ... ... . 19*80 
Lime 6*58 
Magnesia ... ... ... ... ... ... ... 3*61 
Loss on ignition ... ... ... ... ... ... 4*20 
99*89 
In these analyses the lime and magnesia probably belonged to some 
ferro-magnesian mineral, which was subsequently transformed into 
what is given here as “ decomposed ferrugineous mineral,” the advanced 
state of decomposition preventing its determination. 
