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 IJ 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 la}^er. 
26*8 per cent. 
57*6 
17-2 „ 
Organic matter 
Insoluble residue 
Iron oxide 
73*70 
13*64 
10*00 per cent 
97*34 
101 *6 
