56 BATHYMETRICAL SURVEY OF 



The area of the bottom of the loch between the shore and the 

 50-feet line is estimated at about 880 acres (or 19 per cent, of the total 

 area of the loch), that between the 50-feet and 100-feet contours is 

 estimated at 695 acres (or 15 per cent.) ; that between the 100- and 

 200-feet contours is estimated at about 1160 acres (or 25 per cent.); 

 that between the 200- and 300-feet contours at about 875 acres (or 19 

 per cent.) ; that between 300 and 400 feet at 476 acres (or over 10 per 

 cent.) ; that between 400 and 500 feet at about 474 acres (or over 10 

 per cent.); and that over 500 feet at 58 acres (or 1J per cent.). 



It will thus be seen that Loch Ericht is of very simple conformation. 

 The deeper parts are divided into two basins, by the constriction in the 

 outline of the loch in the vicinity of Loch Ericht Lodge, where, in one 

 place, it is less than a quarter of a mile in width, but even here the 

 depth in the centre exceeds 100 feet. 



Deposits. The deposits from Loch Ericht are interesting because of 

 the evidence of layers of different colours. At a depth of 50 feet a red 

 sandy mud was obtained; at 112 feet the mud was white beneath and 

 brown on top; at 124 feet it was all brown; at 153 feet all brown; at 

 182 feet sandy and white ; at 184 feet white and brown ; at 245 feet the 

 deposit was a light-coloured mud, with a thin brown layer one inch in 

 thickness on the top; at 270 feet it was white below, black-brown 

 above ; at 366 feet the mud was all dark brown ; at 385 feet there was a 

 white clay or mud with a dark layer on the top; at 456 feet the mud 

 was all black ; at 497 feet a section of black mud 5 inches in thickness 

 was obtained; and at 510 feet the same black mud was found, without 

 any trace of the lighter-coloured mud. 



The sand from 50 feet consisted largely of mineral particles (pro- 

 bably 70 per cent, of the whole deposit) with a mean diameter of about 

 0-6 mm., one or two rock fragments attaining a diameter of 7 mm. The 

 remainder of the deposit consisted of clayey and vegetable matter, with 

 minute mineral particles less than 0*05 mm. in diameter, Diatoms, 

 Sponge spicules, and Entomostracous skeletal remains. The light-brown 

 mud from 150 feet contained about 30 per cent, of mineral particles, 

 with a mean diameter of 0'5 mm., the largest being 5 mm. in diameter, 

 with clayey and vegetable matter, and organic remains as previously 

 mentioned. The dark-brown mud from 366 feet contained only about 

 10 per cent, of mineral particles (quartz, black and white mica, &c.) 

 exceeding 0-05 mm. in diameter, the mean diameter being about 0-2 mm. 

 Samples of the two different-coloured layers of mud from a depth of 

 385 feet were submitted to analysis, with the following results : 



Bottom layer. Top layer. 



Organic matter lO'OO per cent 26 '8 per cent. 



Insoluble residue .. ... 73*70 ,, 57'6 ,, 



Iron oxide 13'64 ,, 17'2 ,, 



97-34 101-6 



