216 THE FRESH-WATER LOCHS OF SCOTLAND 
and brittle, gradually crumbling to powder, apparently without the 
generation of obnoxious gas. Large woody stems become very hard 
and black. Putrefaction in this case appears not to take place, but 
rather a kind of desiccation — if one may apply this term to a sub- 
aqueous process. Likewise the mud from the bottom of Loch Ness 
has not the slightest offensive odour, neither does it stain one's hands 
as the fetid kind does. Another cause for the difference existing 
between the lakes of the two areas under consideration is, that in the 
deeper waters of the Ness Area there is a large portion of the bottom 
of the lochs quite destitute of aquatic vegetation. The scattered 
organic detritus is therefore comparatively much less there than in 
the shallow lakes at Nairn, which have an abundant vegetation all over 
their bottoms. The refuse-eating fauna and bacteria existing at 
the bottom are consequently in the former case able to maintain an 
equilibrium between supply and demand, and the lake bottom consists 
essentially of the non-fetid excrement of these creatures. In lakes 
whose floor is wholly carpeted with vegetation, the supply of organic 
detritus is greatly in excess of the demand of any refuse-eating fauna 
that may exist, and therefore fetid mud results from the processes of 
unhindered decomposition. In these lakes there is little evidence of 
lime, and little or no acid peat extract. The water is somewhat 
stagnant, and, from the considerable amount of decomposing organic 
matter, it presents a turbid and unwholesome appearance. In these 
respects this district again differs from the two former Areas considered. 
In consequence of the depressed situation, and with surrounding forest, 
these lakes are much sheltered from wind. Although in close proximity 
to the sea, the water is not brackish. 
The littoral vegetation is in general more luxuriant here than in 
the peaty lochs ; it also occurs all around the lochs more or less, and 
not particularly at the west side, as in the lochs of Area I. Five 
illustrations are given in the original paper. 
Loch Cran is about one-third of a mile long, and conforms with 
the description already given. It is very shallow, and has a bottom 
carpet of Chara aspera and Potamogeton heterophyllus over the greater 
portion of it, besides a considerable number of other plants both on 
the bottom and at the margin. 
Loch Loy is somewhat larger than the last-mentioned, being 
about a mile long ; a considerable portion of it, however, is very 
narrow. No boat being available at the time of my visit, I could not 
examine its bottom flora beyond the margins. In this respect it 
probably resembles Loch Cran, but it is said to be deeper. Typha 
latifolia grows abundantly on some parts of its shore. In some places 
the shore is flat, and consists of sandy mud without vegetation. This 
loch is more closed in by trees than the last- mentioned, and at one part 
