42f> 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) Yellow-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 O'l 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 O'l 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. 



