Dr MacCulloch on Peat 
49 
tract by which Loch Greinord communicates with the head of 
Loch-in-daal, and the stratum of maritime peat is here sub- 
merged beneath a considerable depth of alluvial soil. 
In North Uist, peat is found in analogous situations, appear- 
ing, in these cases, to have been generated by those plants which 
grow in sandy soils, and which have, after a certain time, been 
overwhelmed by the accumulation of blown sand. The sub- 
mergence of maritime peat by soil, where the estuary of a ri- 
ver is the sea, is so exactly analogous to that which takes place 
where a river terminates in a lake, that it is unnecessary to dwell 
on it. It is equally obvious, that the power which the semi- 
maritime plants exert in detaining the alluvia of rivers, or the 
sand of the sea-shore, is similar to that which the common reed 
and bulrush exert on the shores of lakes, and it is therefore 
also unnecessary to dwell on this subject. As the marl of 
fresh-water shells is found alternating with inland peat, so de- 
posites of sea^shells, in various states, are found intermixed with 
that which is of maritime origin. 
The peat formed on sea-shores by the plants that grow in 
sand, is small in quantity ; nor is it always certain that it ori- 
ginates in these plants, even where it is difficult to discover to 
what others it can have owed its origin. These plants are 
chiefly the following : 
Triticum junceum. 
Elymus arenarius. 
Arundo arenaria. 
Carex arenaria. 
Galium verum. 
Valantia cruciata. 
Thalictrum minus. 
Trifolium repens ; and various 
well known grasses. 
The plants which grow on the alluvial flats, or in the salt- 
marshes, are more numerous, and comprise principally the fol- 
lowing species : 
Glaux maritima. 
Juncus maritimus. 
Triglochin maritimum. 
Aster tripolium, 
Schoenus mariscus. 
Arenaria peploides. 
marina. 
Scirpus holoschcenus. 
maritimus. 
But the most conspicuous 
alluvia of maritime 
Scirpus triqueter. 
Matricaria maritima. 
Statice limonium. 
armeria. 
Artemisia maritima. 
Bunias cakile. 
Chenopodium maritimum. 
Salicornia herbacea. 
fruticulosa. 
and important plant in extending the 
estuaries, is the Zostera marina^ which forms 
V OL. II. NO. 3. JANUARY 1820. 
D 
